312C, 315C, 318C, 319C, 320C, 322C, 325C and 330C Excavators Air Conditioning and Heating Caterpillar

Troubleshooting the System with the Manifold Gauge Set

Illustration 1	g00862735
(1) Power switch (2) Automatic temperature control switch (3) Air conditioning override switch (4) Temperature selection switches (5) Preset temperature display (6) Fan speed switches (7) Air outlet selection switch (8) Air inlet selection switch (9) Control panel (10) Defrost switch

The following conditions must exist in order to perform the checking procedures:

Engine ... Normal operating temperature

Door ... Open

Air inlet selection switch (8) ... Recirculation

Temperature of air at inlet ... 30° to 35°C (86° to 95°F)

Fan speed switch (6) ... HI

Engine rpm ... 1500 rpm

Temperature selection switch (4) ... MAXCOOL

The following readings are correct under normal operating conditions.

Illustration 2	g00475933
(L) Low pressure side 0.15 to 0.25 MPa (22 to 36 psi) (H) High pressure side 1.37 to 1.57 MPa (200 to 230 psi)

Problem: The system has an insufficient amount of refrigerant charge.

Symptoms:

• Pressure is low on the low side and the high side.

• Bubbles continuously appear in the sight glass.

• The cooling effect is poor.

Cause: A refrigerant leak exists. This leak causes the amount of refrigerant charge to be low.

Corrective Measures:

1. Isolate the leak and repair the refrigerant leak.

2. Recharge the air conditioning system. Refer to the Testing and Adjusting, "Refrigerant System - Charge" section for the proper procedure.

Problem: The system is overcharged with refrigerant. This causes poor cooling by the condenser.

Symptoms:

• Pressure is high on the low side and the high side.

• Bubbles do not appear in the sight glass even when the system is operated slowly.

• The cooling effect is poor.

Cause: The system is overcharged with refrigerant and the condenser is not cooling well.

Corrective Measures:

1. Recover the refrigerant until the level is correct. Refer to the Specifications, "System Capacities for Refrigerant" section for the proper amount of charge.

2. Clean the condenser.

3. Check the engine cooling fan.

Problem: Moisture is present in the refrigerant circuit.

Symptom:

• After a few minutes of use, the low pressure side gradually indicates negative pressure.

Cause: Moisture has entered the refrigerant circuit.

Corrective Measures:

1. Replace the receiver-dryer. Refer to the Operation and Maintenance Manual, "Refrigerant Receiver-Dryer - Replace" section for the proper procedure.

2. Evacuate the system. Refer to the Testing and Adjusting, "Refrigerant System - Evacuate" section for the proper procedure.

3. Charge the system. Refer to the Testing and Adjusting, "Refrigerant System - Charge" section for the proper procedure.

Problem: The compressor is supplying insufficient compression.

Symptoms:

• The manifold gauge set shows excessive high pressure on the low side.

• The high pressure side measures pressure that is too low.

• Pressure equalizes when the compressor is turned OFF.

Cause: The compressor is failing.

Corrective Measure: Check and repair the compressor.

Problem: The refrigerant does not circulate properly.

Symptoms:

• Negative pressure is indicated immediately on the low side when the system is completely clogged.

• Negative pressure is indicated gradually on the low side when the system is sometimes clogged.

• Air temperature is different before clogging and after clogging.

Cause: There is debris collecting around the small holes of the expansion valve. It is also possible that moisture is freezing around the expansion valve.

Corrective Measures:

1. Replace the receiver-dryer. Refer to the Operation and Maintenance Manual, "Refrigerant Receiver-Dryer - Replace" section for the proper procedure.

2. Evacuate the system. Refer to the Testing and Adjusting, "Refrigerant System - Evacuate" section for the proper procedure.

3. Charge the system. Refer to the Testing and Adjusting, "Refrigerant System - Charge" section for the proper procedure.

Problem: Air is present in the refrigerant circuit.

Symptoms:

• Pressure is high on both sides of the manifold gauge set.

• The low pressure lines are not cold.

• Bubbles appear at the sight glass.

Cause: The refrigerant circuit contains air.

Corrective Measures:

1. Recover the refrigerant. Refer to the Testing and Adjusting, "Refrigerant Recovery" section for the proper procedure.

2. Evacuate the system. Refer to the Testing and Adjusting, "Refrigerant System - Evacuate" section for the proper procedure.

3. Charge the system. Refer to the Testing and Adjusting, "Refrigerant System - Charge" section for the proper procedure.

Problem: The expansion valve is not opening properly.

Symptoms:

• Pressure is high on both sides of the manifold gauge set.

• The low pressure lines are frosting.

Cause: The expansion valve is malfunctioning.

Corrective Measure: Make sure that the thermal tube is installed correctly.

Troubleshooting Abnormal Noises

Table 1

Troubleshooting Abnormal Noises
Component	Possible Cause
V-Belt	Tension is low. The belt is loose.
Magnetic clutch	The bearing is worn or the bearing is damaged.
	Contact exists between the stator and the rotor.
Idle pulley	Incorrect installation
	The bearings are worn or the bearings are damaged.
Blower motor	Foreign material is obstructing proper movement.
	The blower is loose.
Compressor	A mounting bolt is loose.
	Valves are bad.
	The bearing is worn or the bearing is damaged.
	Misalignment
Refrigerant lines	Mounting clamps are loose or installed incorrectly.
	Incorrect gap for safety

Troubleshooting the Air Conditioning System

Illustration 3	g00862762
Heater/Air conditioner unit

Problem: The blower motor is nonfunctional and no error code exists.

1. Check the main fuse (20 Amp).

   Expected result: The fuse is good.

   Results:

   • OK - Proceed to step 2.

   • NOT OK - Check the circuit and replace the fuse as required.

2. Check air conditioner clutch relay (19) .

   Expected Result: The relay is functioning properly.

   Results:

   • OK - Proceed to step 3.

   • NOT OK - Replace relay (19) .

3. Unplug the blower motor. Increase the fan speed until the highest fan speed is attained. Check that voltage (24V) is present at wire 2-PK/BU at the blower motor.

   Reference: Refer to the Testing and Adjusting, "Air Conditioning System Schematic" section for the proper wiring diagram.

   Expected result: Voltage is present.

   Results:

   • OK - Proceed to step 4.

   • NOT OK - Replace the (BLC) (18) .

4. Check that ground is present at wire 2-GN/RD at the blower motor.

   Expected Result: Ground is present.

   Results:

   • OK - Proceed to step 5.

   • NOT OK - If ground is not present, proceed to step 6.

5. Apply voltage (24V) to the blower motor.

   Expected Result: The motor turns without excessive noise, vibration or blower wheel rubbing.

   Results:

   • OK - Replace the (BLC) (18) .

   • NOT OK - If the motor does not turn properly, repair the obstruction. If no obstruction exists, replace the blower motor.

6. Check the signal output of the control panel.

   Expected Result: The control panel is correct.

   Results:

   • OK - A wiring problem exists. Check the wiring harness and the connectors. Repair any problems that are found.

   • NOT OK - Replace the control panel.

Problem: The blower motor rotates at high speed only.

1. Check all fan speeds. If the blower rotates only when the HI fan speed is chosen, the BLC (blower linear control) is bad.

   Expected Result: The (BLC) is bad.

   Results:

   • OK - Replace the (BLC) (18) .

   • NOT OK - Refer to "Problem: The blower motor is non-functional and no error code exists."if the blower does not rotate at any speed.

Problem: Air flow to the cab is weak because the blower motor is rotating slowly.

Illustration 4	g00862762
Heater/Air conditioner unit

1. Check for voltage (24V) at the blower motor.

   Reference: Refer to Testing and Adjusting, "Air Conditioning System Schematic" for the proper wiring diagram.

   Expected Result: The proper voltage is present.

   Results:

   • OK - Proceed to step 2.

   • NOT OK - Test the battery and the charging system. Repair if problems are found.

2. Check for poor contacts at the battery terminals.

   Expected Result: The contacts are good.

   Results:

   • OK - Proceed to step 3.

   • NOT OK - Repair the bad contacts and re-test the system.

3. Check the relay for HI fan speed.

   Expected Result: Relay (19) is bad.

   Results:

   • OK - Replace the relay.

   • NOT OK - Replace blower motor (11). The fan wheel is part of the blower motor.

Problem: Air flow to the cab is weak but the blower motor rotates correctly.

Illustration 5	g00862762
Heater/Air conditioner unit

1. Check the fresh air filter and the recirculation filter for clogging.

   Expected Result: The filters are not clogged (dirty).

   Results:

   • OK - Proceed to step 2.

   • NOT OK - Clean the filters and test the system.

2. Check the air inlet for an obstruction.

   Expected Result: The air inlet is not obstructed.

   Results:

   • OK - Proceed to step 3.

   • NOT OK - Remove the obstruction.

3. Make sure that the fan wheel is not distorted or damaged.

   Expected Result: The fan wheel is not damaged.

   Results:

   • OK - Proceed to step 4. The evaporator is freezing.

   • NOT OK - Replace blower motor (11). The fan wheel is part of the blower motor.

4. Stop operating the air conditioner in order to check the voltage at the magnetic clutch.

   Expected Result: Voltage is supplied at the magnetic clutch.

   Results:

   • OK - Proceed to step 5.

   • NOT OK - Replace the magnetic clutch.

5. Check the a/c clutch relay.

   Reference: Refer to the Testing and Adjusting, "Air Conditioning System Schematic" section for the proper wiring diagram.

   Expected Result: The relay is functioning properly.

   Results:

   • OK - Proceed to step 6.

   • NOT OK - Replace the a/c clutch relay.

6. Make sure that the evaporator sensor does not have a short circuit.

   Expected Result: A short circuit does not exist.

   Results:

   • OK - Proceed to step 7.

   • NOT OK - Repair the short circuit.

7. Check the resitance of the evaporator sensor (12) .

   Reference: Refer to the Systems Operation, "Air Conditioning and Heating System Sensor Operation" section for a graph that shows resistance versus temperature figures for this sensor.

   Expected Result: The evaporator sensor is good.

   Results:

   • OK - Proceed to step 8.

   • NOT OK - Replace evaporator sensor (12) .

8. Check the adjustment of the evaporator gap. The gap should be 12 ± 5 mm (0.47 ± 0.20 inch).

   Expected Result: The gap is correct.

   Results:

   • OK - Make sure that the surface of the evaporator is clean. Re-test the air conditioning system for cooling effect.

   • NOT OK - Adjust the gap and re-test the air conditioning system for cooling effect.

Problem: Cool air is not provided because the refrigerant compressor does not rotate normally.

1. Check the V-belt for abnormal wear. Also make sure that the belt does not slip.

   Expected Result: The belt is not worn and the belt does not slip.

   Results:

   • OK - Proceed to step 2.

   • NOT OK - Replace the V-belt.

2. Make sure that the refrigerant compressor is not locked up.

   Expected Result: The compressor functions properly.

   Results:

   • OK - Proceed to step 3.

   • NOT OK - Replace the compressor if it is locked up.

3. Check the functionallity of the magnetic clutch. The following problems could exist:
   • The stator coil could be open circuited.

   • The air gap between the rotor and the stator is too large.

   • The magnetic cluth slips due to an oily clutch surface or a broken key. A short circuited stator coil could also cause the clutch to slip.

   • Debris is caught between the rotor and the stator.

   Expected Result: These situations do not exist.

   Results:

   • OK - Proceed to step 4.

   • NOT OK - Repair the problem with the magnetic clutch or replace the magnetic clutch.

4. Make sure that the magnetic clutch is engaged by the electrical system. Check the wiring.

   Reference: Refer to the Testing and Adjusting, "Air Conditioning System Schematic" section for the wiring information.

   Expected Result: The magnetic clutch is receiving the proper voltage.

   Results:

   • OK - Repeat step 2.

   • NOT OK - Proceed to step 5.

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Illustration 6	g00862735
Control panel (heater/air conditioner unit)

5. Check the following list of electrical problems:
   • Failure of the air conditioning override switch (3)

   • Failure of the fan speed switch (6)

   • Failure of the a/c clutch relay

   • Failure of the water temperature sensor (thermo sensor)

   • Failure of the high/low pressure switch

   Expected Result: None of these problems exists.

   Results:

   • OK - Proceed to step 6.

   • NOT OK - Replace the failed component and re-test the system.

6. Check the refrigerant pressure on the high side.

   Expected Result: The pressure is abnormally high at 2450 kPa (355 psi) or more.

   Results:

   • OK - Refer to "Problem: The cooling effect is poor due to abnormal high side pressure." for the proper procedure.

   • NOT OK - Also refer to "Problem: The cooling effect is poor due to abnormal high side pressure." if the pressure is low at 980 kPa (142 psi) or less.

Problem: The system blows warm air regardless of the temperature setting.

1. Make sure that all windows and doors are closed.

   Expected Result: All windows and doors are closed.

   Results:

   • OK - Proceed to step 2.

   • NOT OK - Close the open window so that the damper for recirculation vs. fresh air will operate correctly.

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Illustration 7	g00862762
Heater/Air conditioner unit

2. Check the damper motor for temperature control (21). Make sure that the link is engaged so that the dampers move when the motor moves.

   Expected Result: The damper motor functions properly.

   Results:

   • OK - An obstruction is keeping the dampers from closing against the heater core. Remove the obstuction and check for proper movement of the dampers.

   • NOT OK - Replace damper motor (21) .

Problem: The cooling effect is poor due to abnormal high side pressure.

1. Check the refrigerant pressure on the high side.

   Expected Result: The pressure is abnormally high and the pressure cutoff switch sometimes works.

   Results:

   • OK - Proceed to step 2.

   • NOT OK - Proceed to step 4 if the pressure is abnormally low at 980 kPa (142 psi) or less.

Note: An abnormally high ambient temperature can cause high pressure.

2. Make sure that the refrigerant condenser is clean and free of debris.

   Expected Result: The condenser is clean.

   Results:

   • OK - Proceed to step 3.

   • NOT OK - Clean the condenser thouroughly with water.

3. Check the system for an overcharge of refrigerant.

   Reference: Refer to "Problem: The system is overcharged with refrigerant. This causes poor cooling by the condenser." for further information.

   Expected Result: The amount of refrigerant charge is correct.

   Results:

   • OK - Air is evident in the refrigerant circuit. Evacuate the system. Refer to the Testing and Adjusting, "Refrigerant System - Evacuate" section for the proper procedure. When the evacuation is complete, recharge the system. Refer to the Testing and Adjusting, "Refrigerant System - Charge" section for the proper procedure.

   • NOT OK - Recover the refrigerant until the level is correct.

Note: An abnormally low ambient temperature can cause low pressure.

4. Check the system for an undercharge of refrigerant.

   Reference: Refer to "Problem: The system has an insufficient amount of refrigerant charge." for further information.

   Expected Result: The system is charged correctly.

   Results:

   • OK - Proceed to step 5.

   • NOT OK - Perform a leak test and charge the system to the correct level. Refer to the Testing and Adjusting, "Refrigerant Leakage - Test" section for the proper procedures. Be sure to repair any leaks that are found before you charge the system.

5. Check the compressor for proper functionallity. The following problems could exist:
   • Locked shoe of cam plate

   • Locked piston

   • Failed suction valve

   • Failed delivery valve

   Expexted Result: The compressor functions properly.

   Results:

   • OK - The expansion valve has failed. Replace the expansion valve. If temporal clogging has caused a frozen expansion valve, moisture is mixed in the refrigerant circuit. If this situation exists, replace the receiver-dryer and the expansion valve. You must evacuate the system and recharge the system after these repairs are made.

   • NOT OK - Replace the compressor.

Problem: The cooling effect is poor due to abnormal low side pressure.

1. Check the refrigerant pressure on the low side.

   Expected Result: The pressure is abnormally high. The pressure measures approximately 290 kPa (42 psi) or more.

   Results:

   • OK - Proceed to step 2.

   • NOT OK - Proceed to step 5 if the pressure is approximately 50 kPa (7.5 psi) or less..

2. Check the system for an overcharge of refrigerant.

   Reference: Refer to "Problem: The system is overcharged with refrigerant. This causes poor cooling by the condenser." for further information.

   Expected Result: The amount of refrigerant charge is correct.

   Results:

   • OK - Proceed to step 3.

   • NOT OK - Recover the refrigerant until the level is correct. Refer to the Testing and Adjusting, "Refrigerant Recovery" section for the proper procedure.

3. Check the compressor for proper functionallity. The following problems could exist:
   • Bad gasket at the head of the compressor

   • Failed suction valve

   • Debris cought in the suction valve

   Expected Result: The compressor functions properly.

   Results:

   • OK - The opening of the expansion valve is too great. Proceed to step 4.

   • NOT OK - Replace the compressor.

4. Check the contact of the thermal tube.

   Expected Result: The thermal tube is correct.

   Results:

   • OK - Replace the expansion valve.

   • NOT OK - Repair the poor contact of the thermal tube.

Note: An abnormally low ambient temperature can cause low pressure.

5. Check the system for an undercharge of refrigerant.

   Reference: Refer to "Problem: The system has an insufficient amount of refrigerant charge." for further information.

   Expected Result: The system is charged correctly.

   Results:

   • OK - Proceed to step 6.

   • NOT OK - Perform a leak test and charge the system to the correct level. Refer to the Testing and Adjusting, "Refrigerant Leakage - Test" section for the proper procedures. Be sure to repair any leaks that are found before you charge the system.

6. Check the receiver-dryer for clogging.

   Expected Result: The receiver-dryer is not clogged.

   Results:

   • OK - Proceed to step 7.

   • NOT OK - Replace the receiver-dryer.

7. Check for a clogged expansion valve and check for a gas leak at the thermal tube.

   Expected Result: The expansion valve is functioning properly.

   Results:

   • OK - Proceed to step 8. The evaporator is freezing.

   • NOT OK - Replace the expansion valve. If temporal clogging has caused a frozen expansion valve, moisture is mixed in the refrigerant circuit. If this situation exists, replace the receiver-dryer and the expansion valve. You must evacuate the system and recharge the system after these repairs are made.

8. Stop operating the air conditioner in order to check the voltage at the magnetic clutch.

   Expected Result: Voltage is supplied at the magnetic clutch.

   Results:

   • OK - Proceed to step 9.

   • NOT OK - Replace the magnetic clutch.

9. Check a/c clutch relay (19) .

   Reference: Refer to the Testing and Adjusting, "Air Conditioning System Schematic" section for the proper wiring diagram.

   Expected Result: The relay is functioning properly.

   Results:

   • OK - Proceed to step 10.

   • NOT OK - Replace a/c clutch relay (19) .

10. Make sure that the evaporator sensor does not have a short circuit.

    Expected Result: A short circuit does not exist.

    Results:

    • OK - Proceed to step 11.

    • NOT OK - Repair the short circuit.

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Illustration 8	g00862762
Heater/Air conditioner unit

11. Check the resitance of the evaporator sensor (12) .

    Reference: Refer to the Systems Operation, "Air Conditioning and Heating System Sensor Operation" section for a graph that shows resistance versus temperature figures for this sensor.

    Expected Result: The evaporator sensor is good.

    Results:

    • OK - Proceed to step 12.

    • NOT OK - Replace evaporator sensor (12) .

12. Check the adjustment of the evaporator gap. The gap should be 12 ± 5 mm (0.47 ± 0.20 inch).

    Expected Result: The gap is correct.

    Results:

    • OK - Make sure that the surface of the evaporator is clean. Re-test the air conditioning system for cooling effect.

    • NOT OK - Adjust the gap and re-test the air conditioning system for cooling effect.

Problem: The cooling effect is poor due to high pressure on both sides.

Note: If both sides indicate low pressure, the refrigerant is bad. Recover the old refrigerant. Refer to the Testing and Adjusting, "Refrigerant Recovery" section for the proper procedure. Recharge the system with new refrigerant. Refer to the Testing and Adjusting, "Refrigerant System - Charge" section for the proper procedure.

1. Make sure that the refrigerant condenser is clean and free of debris.

   Expected Result: The condenser is clean.

   Results:

   • OK - The air conditioning system is overcharged. Recover the refrigerant until the level is correct. Refer to the Specifications, "System Capacities for Refrigerant" section for the correct amount of charge.

   • NOT OK - Clean the condenser thouroughly with water.

Problem: Air is not provided to the proper air outlet for discharge.

Illustration 9	g00862762
Heater/Air conditioner unit

Note: The following test pertains to the following two damper motors:

• Foot versus defroster (under seat / defroster) (20)

• Fresh air versus recirculated air (22)

1. Check the rotation of the damper motor that is in question.

   Expected Result: The motor rotates normally.

   Results:

   • OK - Proceed to step 2.

   • NOT OK - Proceed to step 3.

2. Make sure that the link arm between the motor and the damper door is engaged. Remove any foreign material as well.

   Expected Result: The link is engaged.

   Results:

   • OK - Proceed to step 3.

   • NOT OK - Engage the link.

3. Check the voltage (12V) at the wiring harness for the damper motor in question.

   Reference: Refer to the Testing and Adjusting, "Air Conditioning System Schematic" section for the proper wiring diagram.

   Expected Result: Voltage is present.

   Results:

   • OK - Replace the damper motor.

   • NOT OK - Proceed to step 4 if voltage is not present.

4. Check the continuity of the wiring harness between the control panel and the damper motor.

   Reference: Refer to the Testing and Adjusting, "Air Conditioning System Schematic" section for the proper wiring diagram.

   Expected Result: Continuity is correct.

   Results:

   • OK - Replace the control panel.

   • NOT OK - Repair or replace the wiring harness as required if the continuity is not correct.

Water is leaking into the cab from behind the seat.

When water enters the cab from the heater/air conditioner unit, the drain on the bottom of the unit is clogged. Remove any obstruction from the drain hole and the problem will be corrected.