Air Conditioning and Heating R-12 All Caterpillar Machines - Air Conditioning System Troubleshooting

Personal injury can result from contact with refrigerant.

This system is under pressure at all times, even if the engine is not running. Heat should never be applied to a charged system.

Contact with refrigerant can cause frost bite. Keep face and hands away to help prevent injury.

Protective goggles must always be worn when refrigerant lines are opened, even if the gauges indicate the system is empty of refrigerant.

Always use caution when a fitting is removed. Slowly loosen the fitting. If the system is still under pressure, evacuate the system recovering the refrigerant before removing the fitting.

Personal injury or death can result from inhaling refrigerant through a lit cigarette.

Inhaling air conditioner refrigerant gas through a lit cigarette or other smoking method or inhaling fumes released from a flame contacting air conditioner refrigerant gas, can cause bodily harm or death.

Do not smoke when servicing air conditioners or wherever refrigerant gas may be present.

Before any checks of the air conditioning and heating system are made, move the machine to a smooth horizontal surface. Lower all implements to the ground. Make sure the transmission is in neutral or park and that the parking brake is engaged. Keep all other personnel away from the machine or where they can be seen.

System Contamination

The system must be cleaned and the system must be flushed if any particles of metal or other foreign material from a component failure have circulated through the system.

Debris in the system can cause the compressor to fail. Use the following procedure for cleaning and flushing the system.

Identify the refrigerant and then recover the refrigerant. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section.

Remove the compressor. Refer to Disassembly and Assembly, SENR3334, “Refrigerant Compressor – Remove and Install”.

Remove the receiver-dryer or the in-line dryer. Refer to Disassembly and Assembly, SENR3334, “Receiver-Dryer – Remove and Install”. Refer to Disassembly and Assembly, SENR3334, “In-Line Refrigerant Dryer – Remove and Install”.

Remove the accumulator. Refer to Disassembly and Assembly, SENR3334, “Refrigerant Accumulator – Remove and Install”.

Remove the expansion valve or the orifice tube. Refer to Disassembly and Assembly, SENR3334, “Refrigerant Expansion Valve – Remove and Install”.

Remove the quick couplers.


NOTICE
In order to avoid component damage, do not clean system components with solvents, compressed air, etc..

NOTICE

In order to avoid component damage, do not clean system components with solvents, compressed air, etc..

Replace any other failed component such as coils, fittings, etc. Flush the remainder of the system. The air conditioning system should be flushed with a 153-8537 Air Conditioner Flushing Unit. Also, a 153-9032 Air Conditioner Flushing Unit can be used in order to flush the system. Refer to the information that is provided with the flushing unit. Flush the system with 153-8538 Refrigerant Flushing Solution .

Blow out the air conditioning system with dry shop air for 5 to 10 minutes.

Install a new receiver-dryer or an in-line dryer. Refer to Disassembly and Assembly, SENR3334, “Receiver-Dryer – Remove and Install”. Refer to Disassembly and Assembly, SENR3334, “In-Line Refrigerant Dryer – Remove and Install”.

Install a new accumulator. Refer to Disassembly and Assembly, SENR3334, “Refrigerant Accumulator – Remove and Install”.

Replace the original orifice tube. Clean the expansion valve or replace the expansion valve. Clean the original quick couplers or replace the original quick couplers.

Install a new compressor. New compressors are shipped with the correct amount of oil inside the compressor. Do not add extra oil. Refer to Disassembly and Assembly, SENR3334, “Refrigerant Compressor – Remove and Install”.
Note: Compressors that are new or remanufactured are shipped with the correct amount of refrigerant oil in the system.

False Seizure of the Compressor

Table 1
Required Tools
Part Number	Part Description
1U-8590	Spanner Wrench

On the initial start-up of the air conditioner system, slipping drive belts and broken drive belts may be experienced if the air conditioner system has not been used for an extended period of time. Also, scored clutch surfaces may be experienced. This would indicate a seized compressor. However, replacement of the compressor may not be necessary.

Changes in temperature can cause expansion of the refrigerant in the compressor during extended periods of nonuse. Also, changes in temperature can cause contraction of the refrigerant in the compressor during extended periods of nonuse. During this movement, lubricating oil that is carried by the refrigerant migrates. The lubricating oil moves away from highly polished surfaces in the compressor. Without lubricating oil at the polished surfaces, the polished surfaces rub together. This can appear as a seized compressor.

The compressor should be checked for seizure before the compressor is replaced. Use the procedures that follow in order to check the compressor for seizure.

With a spanner wrench on the clutch drive plate, rock the shaft in the opposite direction of normal rotation.

After the clutch drive plate is movable, rotate the clutch drive plate at least three complete revolutions in the counterclockwise direction.

Start the engine. Operate the compressor for a minimum of one minute.
This procedure will not correct a seized compressor. However, this procedure should be attempted before you replace a compressor that has been idle for a month or longer.

Performance Checks for the Air Conditioning System

A performance check of the air conditioning system must be made with a manifold gauge set. The manifold gauge set must be connected to the service ports on the compressor.

Note: Before you conduct a performance check, refer to the Service Manual, SENR3334, “Visual Inspection for all Machines” section.

Refer to the Service Manual, SENR3334, “Machine Preparation for Troubleshooting” section before service work is performed on the air conditioning system.

Install the manifold gauge set. Refer to the Service manual, SENR3334, “Installing the Manifold Gauge Set” section.

Start the engine and operate the engine at 1000 rpm. Move the temperature control knob to the maximum cool position. Put the fan switch in the HIGH position on the AIR CONDITIONING side. In order to stabilize the system, operate the system for a minimum of ten minutes. Operate the engine at 1000 rpm.
During normal operation of the air conditioning system in 21°C (70°F) weather, the discharge pressure will be 820 to 1300 kPa (120 to 190 psi). The pressure will be 70 to 130 kPa (10 to 20 psi). Refer to Table 2 for temperature range. The outside temperature and humidity will have an effect on the pressures. If the outside temperature is high, the discharge pressure will be high.

In very hot weather, the suction and the discharge pressures will be high. In cooler weather, the suction and the discharge pressure will be normal or the pressure can be lower.

If the suction and the discharge pressures are not within the normal operating range, refer to the “Problem Solving” section.

Note: Most system failures are caused by improper refrigerant charge. Refrigerant charge should be measured by weight only. Do not use gauge pressure when you charge the system with refrigerant.

Problem Solving

The following problem solving section is provided for identifying and correcting problems that may occur in the air conditioning system. Several problems can have the same system condition or similar system conditions. Before you start the procedure in order to correct the problems, it is necessary to be complete in the diagnosis of the problems.

The problem solving procedures are based on the system condition during the problem. In order to indicate the system pressures, the manifold gauge set must be installed. The manifold gauge set is used only in order to diagnose problems. The refrigerant lines can give an indication of system operation that is abnormal. Temperature differences between the high pressure side and the low pressure side can be an indication of abnormal operation in a line. This can also be found by cold spots (frost) on the line. The temperature of the air flow from the evaporator will also indicate a problem with the system. Knowing the complete system condition is an important step in making a correct diagnosis.

Note: R-12 air conditioning system problem diagnosis requires a combination of symptoms or indicators in order to correctly identify problems and solve problems.

Problem Solving Procedure

Install the manifold gauge set. Refer to the Service Manual, SENR3334, “Installing the Manifold Gauge Set” section in Testing and Adjusting.

Run the engine at 1000 rpm. Put the air conditioner temperature control knob in the Maximum COOL position. Put the fan switch in the HIGH position on the AIR CONDITIONING side. In order to stabilize the system, operate the engine for a minimum of ten minutes.

Place a thermometer near an air vent inside the cab. Record the temperature.

Adjust the engine speed to approximately 1300 to 1400 rpm. Record the readings on the following gauges: low pressure gauges, high pressure gauges and thermometer. The gauge readings will be a partial indication of the system condition.

Note: When the ambient temperature is above 21°C (70°F), a low pressure gauge reading of 70 to 138 kPa (10 to 20 psi) is a normal operating pressure for the air conditioning system. Also, when the ambient temperature is above 21°C (70°F), a high pressure gauge reading of 820 to 1300 kPa (120 to 190 psi) is a normal operating pressure for the air conditioning system. In very hot weather, the low pressure readings and the high pressure readings will be at the high end of the normal operating range. In cooler weather, the low pressure reading will be in the middle to the low end of the normal operating range, while the high pressure reading will be low. For the correct gauge reading in relation to ambient temperature condition, refer to Table 2.

Note: All pressures are given as a guide only. Weight is the only absolute means of determining proper refrigerant charge. Improper refrigerant charge will cause premature failure of the compressor.

Table 2
Pressure Range ⁽¹⁾
Ambient Air Temperature C° (F°)	High Pressure Test Fitting kPa (psi) ⁽²⁾	Low Pressure Test Fitting kPa (psi) ⁽³⁾
21°C (70°F)	820 to 1300 kPa (120 to 190 psi)	50 to 105 kPa (7.25 to 20 psi)
27°C (80°F)	950 to 1450 kPa (140 to 210 psi)	50 to 173 kPa (7.25 to 25 psi)
32°C (90°F)	1175 to 1650 kPa (170 to 240 psi)	50 to 105 kPa (7.25 to 25 psi)
38°C (100°F)	1300 to 1850 kPa (190 to 270 psi)	70 to 210 kPa (10 to 30 psi)
43°C (110°F)	1450 to 2075 kPa (210 to 300 psi)	70 to 210 kPa (10 to 30 psi)

^( 1 )	This table is only for reference.
^( 2 )	Pressure may be slightly higher in very humid conditions and lower in very dry conditions.
^( 3 )	Pressure before clutch disengagement

Refrigerant Circuit Problems

There is no or only little cool temperature to the air flow from the evaporator.

System Condition 1

Low pressure gauge reading is below normal. For normal operating pressures, refer to Table 2.

High pressure gauge reading is below normal. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F).

From the evaporator, the temperature of the air flow is partially cool.

Probable Cause

Leaks in the refrigerant circuit will cause the system to be low on refrigerant.

Perform a leak test. refer to the Service Manual, SENR3334, “Refrigerant Leakage – Test” section in Testing and Adjusting.
If leaks are found, recover the refrigerant. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section.
Repair leaks.
If a large amount of refrigerant was lost, it is important to check the compressor for loss of oil.
Perform a partial charge of the system.
Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in testing and adjusting.
After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

System Condition 2

Low pressure gauge reading is normal. For normal operating pressures, refer to Table 2.

High pressure gauge reading bounces or the reading is unsteady.

Probable Cause

Air is in the system.

Reclaim the refrigerant from the air conditioning system.
Evacuate the air conditioning system.
Recharge the air conditioning system.

System Condition 3

Low pressure gauge reading is below normal. For normal operating pressures, refer to Table 2.

High pressure gauge reading is above normal. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F).

The temperature of the air flow from the evaporator is warm.

Probable Cause

Air or moisture (water) in the system

Recover the refrigerant. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section.
Replace the receiver-dryer or the in-line dryer. The desiccant may be full of moisture. This will release water into the system. Refer to Disassembly and Assembly, SENR3334, “Receiver-Dryer – Remove and Install”. Refer to Disassembly and Assembly, SENR3334, “In-Line Refrigerant Dryer – Remove and Install”.
Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

System Condition 4

Low pressure gauge reading is below normal. For normal operating pressures, refer to Table 2.

High pressure gauge reading is normal to higher than the normal range. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F).

The temperature of the air flow from the evaporator is partially cool.

The high side liquid line or the receiver-dryer is frosted. The high side liquid line or the receiver-dryer is cool to the touch.

Probable Cause

Restriction in the high pressure liquid line can cause the refrigerant to be removed from the evaporator at a faster rate. The restriction can cause the evaporator to be low on refrigerant from the receiver-dryer or from the in-line dryer. Clogged filters or a failure of the blower motor can cause possible restrictions to the air flow.

Recover the refrigerant. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section.
If the restriction is found at the receiver-dryer, replace the receiver-dryer. Refer to Disassembly and Assembly, SENR3334, “Receiver-Dryer – Remove and Install”.
If the restriction is found at the in-line dryer, replace the in-line dryer. Refer to Disassembly and Assembly, SENR3334, “In-Line Refrigerant Dryer – Remove and Install”.
If the restriction is found at the liquid line, replace the liquid line.
Cap all the open lines and fittings.

Note: Restrictions of the refrigerant flow are identified by frost or cold spots in the line. Also, restrictions of the refrigerant flow are identified by frost or cold spots in the receiver-dryer or the in-line dryer.

Replace filters or remove any of the restrictions.
Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

System Condition 5

Note: The system only cools the cab in the morning and in the evening. The system does not cool the cab during the hot part of the day.

Low pressure gauge reading is normal, but the gauge reading may drop into the vacuum range during the testing procedure. For normal operating pressures, refer to Table 2.

The high pressure gauge reading is normal, but the gauge reading is below normal when the low pressure gauge drops into the vacuum range. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F).

Air flow from the evaporator is very cold, but the air flow will become warm when the low pressure gauge drops into vacuum.

Probable Cause

The system has a large amount of moisture. The desiccant in the receiver-dryer or the in-line dryer is full of water. The water is released during high ambient temperatures. Ice collects in the orifice or the expansion valve and the ice can block the flow of refrigerant.

Recover the refrigerant from the system. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section in Testing and Adjusting.
Replace the receiver-dryer or the in-line dryer. Refer to the proper Disassembly and Assembly manual for your machine.
Remove the moisture from the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

Note: Low pressure (suction) drops into vacuum when ice forms in the expansion valve. High pressure (discharge) drops when low pressure drops into vacuum.

System Condition 6

The low pressure gauge reading does not change. The pressure should rise when the compressor is not in operation. For normal operating pressures, refer to Table 2.

High pressure gauge reading is at the high end of the normal range.
Note: Ambient temperature is above 21°C (70°F).

The temperature of the air flow from the evaporator is partially cool.

Probable Cause

The system has air or moisture in the system. The system does not have a full charge of refrigerant.

Perform a leak test and carefully test around the compressor seal. Refer to the Service Manual, SENR3334, “Refrigerant Leakage – Test” section in Testing and Adjusting.
Recover the refrigerant from the system. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section in Testing and Adjusting.
Repair leaks.
Check the compressor for loss of oil.
Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

System Condition 7

Low pressure gauge reading is above normal. For normal operating pressures, refer to Table 2.

High pressure gauge reading is above normal. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F).

High pressure (liquid line) is very hot.

The compressor may become noisy and the drive belt may slip.
Note: The compressor is not operating under ambient temperatures that are extreme. The compressor is not operating under high humidity that is extreme.

Probable Cause

The system is overcharged.

Recover the remaining refrigerant. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section.
Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
Perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

Note: Perform the following procedure if the system has not been serviced for a extended period of time. Perform the following procedure if the pressures of the system are not within the correct specifications.

Recover the refrigerant. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section.
Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting. If service work has not been performed for a extended period of time, replace the receiver-dryer or the in-line dryer.
Charge the system with the correct amount of refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

System Condition 8

Low pressure gauge reading is above normal. For normal operating pressures, refer to Table 2.

High pressure gauge reading is below normal. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F) and the system has a refrigerant charge that is full.

The temperature of the air flow from the evaporator is partially cool.

Probable Cause

The compressor has internal leaks. The reed valve has leakage. The compressor piston, rings or cylinders are worn.

Check the compressor drive belt for the correct tension.
Perform a leak test. Isolate the problem to the compressor. Refer to the Service Manual, SENR3334, “Refrigerant Leakage – Test” section in Testing and Adjusting.

If an internal leak is found, perform the following procedure.

Replace the compressor. Refer to Disassembly and Assembly, SENR3334, “Refrigerant Compressor – Remove and Install”.
Replace the receiver-dryer. Refer to Disassembly and Assembly, SENR3334, “Receiver-Dryer – Remove and Install”.
Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
Charge the system with the correct amount of refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

If an external leak such as a hose connection is found, perform the following procedure.

Recover the refrigerant. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section.
Repair leaks.

If a large amount of refrigerant is lost, check the compressor for the loss of oil.

Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

System Condition 9

Low pressure gauge reading is above normal. For normal operating pressures, refer to Table 2.

High pressure gauge reading is normal or low. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F) and the system has a refrigerant charge that is full.

The temperature of the air flow from the evaporator is warm.

The suction hose and the evaporator is covered with moisture (sweating).

Probable Cause

Flow of refrigerant through the evaporator coil is excessive. The expansion valve could be stuck or held in the OPEN position. The orifice tube is missing in the orifice tube system.

Test the expansion valve for the correct operation. Use the following procedure.
- Position the air conditioner temperature control knob in the maximum COOL position and the fan switch in the HIGH position.
- Cool the head of the expansion valve diaphragm chamber and the capillary tube with ice or liquid nitrogen. Record the low pressure gauge reading. The low pressure gauge should indicate a vacuum.
- If the low pressure gauge indicates a vacuum, place a hand over the expansion valve diaphragm chamber. The hand will warm the expansion valve diaphragm chamber. In order to ensure the correct operation of the expansion valve, cool the head of the expansion valve diaphragm chamber and the capillary tube with ice or liquid nitrogen again. If the operation of the expansion is correct, refer to Step 2.
- If the low pressure gauge does not indicate the proper operation of the expansion valve, recover the refrigerant from the system. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section in Testing and Adjusting.
- Replace the expansion valve. Refer to the proper Disassembly and Assembly manual for your machine.
Note: The sensing bulb must be installed correctly in order to ensure the proper operation of the expansion valve.
- Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
- Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
- After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

If the pressure gauge indicates the correct operation of the expansion valve, perform the following procedure.
- Use a 8P-6355 Clip in order to hold the sensing bulb onto the evaporator outlet pipe. The sensing bulb should be as close to the evaporator as possible. The bulb should be upstream of the pressure sensing connection on the evaporator outlet pipe. The following items must be wound tightly with 5P-7070 Strip Insulation : the clip, the sensing bulb and the outlet pipe. There should be no insulation between the bulb and the outlet pipe.
- In order to ensure that the system operates correctly, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.




Illustration 1	g00409166
Expansion valve in the open position (Typical Example) (1) Capillary tube (2) Expansion valve diaphragm chamber (3) Inlet (4) Outlet

System Condition 10

Low pressure gauge reading is too low. For normal operating pressures, refer to Table 2.

High pressure gauge reading is too low. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F).

The temperature of the air flow from the evaporator is partially cool or warm.

Moisture (water) or frost is on the expansion valve inlet or orifice tube assembly.

Probable Cause

The problems that are described in Step 1 through Step 4 can be caused by the following faults:

Note: The following faults will cause a restriction of the flow of refrigerant to the evaporator.

Improper operation of the expansion valve (stuck valve)
Blockage at the evaporator inlet
No charge in temperature sensing bulb

Note: The inlet to the expansion valve will be warm during normal operation.

If the expansion valve inlet is cool to the touch, perform the following procedure:
- Position the air conditioner temperature control knob to the maximum COOL position and the fan switch to the HIGH position.
- Cool the head of the expansion valve diaphragm chamber and capillary tube with ice or liquid nitrogen. Record the low pressure gauge reading. The low pressure gauge should indicate a vacuum.
- If a vacuum is indicated on the low pressure gauge, place a hand over the expansion valve diaphragm chamber. The hand will warm the expansion valve diaphragm chamber. In order to ensure the correct operation of the expansion valve, cool the head of the expansion valve diaphragm chamber and the capillary tube with ice or liquid nitrogen again. If the operation of expansion valve is correct, refer to Step 2.
- If the low pressure gauge does not indicate proper operation of the expansion valve, remove the refrigerant from the system. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section in Testing and Adjusting.
- Replace the expansion valve. Refer to the proper Disassembly and Assembly manual for your machine.
Note: The sensing bulb must be installed correctly in order to ensure the correct operation of the expansion valve. Clean the location for the sensing bulb with steel wool or emery paper. Use a 8P-6355 Clip in order to attach the sensing bulb securely to the evaporator coil outlet pipe. Completely cover the assembly with 5P-7070 Strip Insulation .
- Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
- Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
- After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

If the low pressure gauge indicates the correct operation of the expansion valve, perform the following procedure:
- The sensing bulb must be in the correct position on the evaporator outlet pipe and the sensing bulb must be the correct distance away from the evaporator outlet. The bulb should be upstream from the pressure sensing connection in the evaporator outlet pipe. The insulation must be around the sensing bulb and the clip on the evaporator outlet pipe.
- In order to ensure the correct systems operation, perform a performance check.

Replace the in-line dryer or replace the orifice tube.
- Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
- Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
- After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.




Illustration 2	g00415456
Expansion valve in the closed position (Typical Example) (1) Capillary tube (2) Expansion valve diaphragm chamber (3) Inlet (4) Outlet

Note: For expansion valve systems, refer to Step 1. For orifice tube systems, refer to Step 3.

System Condition 11

Low pressure gauge reading is too high. For normal operating pressures, refer to Table 2.

High pressure gauge reading is too high. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F).

The temperature of the air flow from the evaporator is warm.

Probable Cause

The condenser is not functioning properly.

Note: The system may have a normal or overcharge of refrigerant.

Check for a blockage in the flow of air through the condenser.

If a blockage is found in the condenser, remove all blockages and perform a performance check. The performance check will ensure proper system operation. Refer to “Performance Checks for the Air Conditioning System” section.

If the problem still exists, perform the following procedure. Check the system for an overcharge of refrigerant.
Note: Do not operate the engine.
- Recover the refrigerant. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section in Testing and Adjusting.
- Evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
- Recharge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
Note: With the ambient temperature above 21°C (70°F), the normal gauge reading for the low pressure side is 70 to 138 kPa (10 to 20 psi) while the normal gauge reading for the high pressure side is 820 to 1300 kPa (120 to 190 psi).
- In order to ensure the correct systems operation, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

If the low pressure gauge reading and the high pressure gauge readings are too high, perform the following procedure:
- Recover the refrigerant from the system. Refer to the Service Manual, SENR3334, “Refrigerant Recovery” section in Testing and Adjusting.
- Replace the receiver-dryer or replace the in-line dryer. Refer to the proper Disassembly and Assembly manual for your machine.
- If the receiver-dryer or the in-line dryer is not equipped with quick couplers, evacuate the system. Refer to the Service Manual, SENR3334, “Refrigerant System – Evacuate” section in Testing and Adjusting.
- Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting.
- After the system is charged and operated for a minimum of ten minutes, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

System Condition 12

Water is in the vents.
Water is leaking from the unit.

Probable Cause

The nonreturn valve of the drain

Check for dirt which may be plugging the drain tube on the evaporator.

Check the nonreturn valve for proper positioning.

Check the nonreturn valve for proper direction.

The Compressor will not Engage

If the machine is equipped with the protection system for the refrigerant compressor, Refer to the Service Manual, SENR 3334, “Troubleshooting Heating and Air Conditioning Control Systems” in order to test the on delay timer assembly for the refrigerant compressor.

System Condition 13

Low pressure gauge reading is above normal. For normal operating pressures, refer to Table 2.

High pressure gauge reading is below normal. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F).

Air flow to the operator’s compartment is warm.

Probable Cause

The thermostatic switch is stuck open. This does not allow the magnetic clutch to cycle the compressor.
1. Check the wire connectors on the thermostatic switch and on the magnetic clutch.

The connection of wire leads on switch is improper. The connection of wire leads on the magnetic clutch is improper.
1. Check for insulation that is broken. The insulation failure can expose the wires from the switch to the magnetic clutch.

The wire that connects the switch to the magnetic clutch has an opening.
1. Check the resistance of the coil with a multimeter. Refer to the Service Manual, SENR3334, “Refrigerant Compressor” section in Specifications for your compressor.
1. Check for the proper electrical ground at the magnetic clutch.
1. Touch the two wires on the switch together. Check for the proper operation of the magnetic clutch.
1. In order to check the electrical components, refer to Service Manual, SENR3334, “Troubleshooting Heating and Air Conditioning Control System” in Testing and Adjusting.
  If the problem is a loose wire on the switch or a loose wire on the magnetic clutch, make the repairs that are needed. If the wires to the clutch were damaged, the damaged wires can cause the switch to remain open. Make the needed repairs to the damaged wires. In order to ensure the correct system operation, perform a performance check.

The charge of refrigerant in the capillary tube (thermostatic switch) has been lost.
1. If the capillary tube has no charge or the switch remains open, the problem is in the thermostatic switch.
  - Replace the switch.
  - In order to ensure the correct system operation, perform a performance check. Refer to “Performance Checks for the Air Conditioning System” section.

The Compressor Continues to Cycle or the Clutch will not Disengage.

Note: The cause of the problem may be one of the following conditions: low charge, overcharge and evaporator freeze-up .

System Condition 14

Low pressure gauge reading is below normal. For normal operating pressures, refer to Table 2.

High pressure gauge reading is below normal. For normal operating pressures, refer to Table 2.
Note: Ambient temperature is above 21°C (70°F).

The air flow to the operator’s compartment is very cold, or the air flow may be restricted completely at times.

Probable Cause

The thermostat switch is held closed. There is a short in the wire to the magnetic clutch. The magnetic clutch will not release.

Check the wire that goes to the magnetic clutch. The wire may have an electrical short.
Replace the thermostat switch or verify the correct placement of the capillary tube.
Make the necessary repairs to the magnetic clutch.

The system is improperly charged.
A compressor drive belt that is loose or a compressor drive belt that is worn can cause insufficient cooling.
Restrictions, insects, foreign material in the condenser, or any restriction of airflow can cause insufficient cooling.
A missing or a plugged orifice tube can cause insufficient cooling.
A restriction in a liquid line or a low amount of refrigerant charge can cause insufficient cooling.

Install the manifold gauge set. Refer to the Service manual, SENR3334, “Installing the Manifold Gauge Set” section.

Start the engine. Operate the engine at 1400 rpm. Move the temperature control knob to the Maximum position and the fan to the High position. Close all windows and doors. In order to stabilize the system, operate the system for a minimum of ten minutes.
Note: Ambient temperature is above 21°C (70°F).

The outlet on the accumulator should be cold to the touch. If the outlet is not cold, check the readings on the manifold gauges.
- If the low side reading is above 345 kPa (50 psi), check for a missing orifice tube.
- If the low side reading is into vacuum, check for a plugged orifice tube or a restriction in the line.
- A restriction in the liquid line can be detected by running a hand along the line until there is a change in temperature. A change in temperature in the line will usually indicate the location of the restriction.

If the inlet and the outlet on the accumulator are warm, refer to the Service Manual, SENR3334, “Refrigerant System – Charge” section in Testing and Adjusting. Also, refer to the Service Manual, SENR3334, “Refrigerant Leakage-Test” section in Testing and Adjusting.

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