312E, 312F, 313F, 316E, 316F, 318E, 318F, 320E, 320F, 323E, 323F, 324E, 325F, 326F, 329E, 329F, 330F, 335F, 336E, 336F, 340F, 349E, 349F, 352F, 374F and 390F Excavators and 336E MHPU and 349E MHPU Mobile Hydraulic Power Units Air Conditioning and Hea Caterpillar

Troubleshooting the Air Conditioning System with the Manifold Gauge Set

Note: Refer to Testing and Adjusting, "Visual Inspection" before you conduct a performance check.

Note: Refer to Testing and Adjusting, "Machine Preparation for Troubleshooting" before you perform service work on the air conditioning system.

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. Complete diagnosis of the problems is necessary before you start the procedure in order to correct 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. In R134a air conditioning systems, the lines can have spots of frost and the system can be operating normally. Frost will most often form after the orifice and on the lower portion of the accumulator. 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: R134a air conditioning system problem diagnosis requires a combination of symptoms or indicators in order to identify problems correctly and solve problems.

Problem Solving Procedure

Illustration 1	g02357316
Control Panel (1) Temperature control switch (increase/decrease) (2) Fan switch (increase/decrease) (3) Air inlet select switch (4) Main power (ON/OFF) switch (5) Preset temperature display (6) Compressor (ON/OFF) switch

1. Install the manifold gauge set. Refer to Testing and Adjusting, "Manifold Gauge Set (Refrigerant) - Install".

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

   1. Run the engine at 1000 rpm.

   2. Turn the control panel ON using main power switch (4).

   3. Turn the refrigerant compressor ON using compressor switch (6).

   4. Set the air conditioner temperature to the maximum cool position using temperature control switch (1).

   5. Set the fan air flow to the maximum position using fan switch (2).

   6. In order to stabilize the system, operate the engine for a minimum of 10 minutes.

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

4. Compare the discharge and suction pressures on the manifold gauge set to the pressure ranges that are in Table 1. Use Table 1 to determine if the system is functioning correctly for the current ambient temperature and to determine if the system is operating normally. If the pressures are high according to the chart or low according to the char, refer to the system conditions that are listed in "Refrigerant Circuit Problems".

   During normal operation of the air conditioning system in 21° C (70° F) weather, the discharge pressure will be 820 kPa (120 psi) to 1300 kPa (190 psi).

   The pressure on the suction side will be 70 kPa (10 psi) to 130 kPa (20 psi).

   The outside temperature and humidity will affect 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.

   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.

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   Table 1

   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)	70 to 138 kPa (10 to 20 psi)
   27° C (80° F)	950 to 1450 kPa (140 to 210 psi)	70 to 173 kPa (10 to 25 psi)
   32° C (90° F)	1175 to 1650 kPa (170 to 240 psi)	105 to 210 kPa (15 to 30 psi)
   38° C (100° F)	1300 to 1850 kPa (190 to 270 psi)	105 to 210 kPa (15 to 30 psi)
   43° C (110° F)	1450 to 2075 kPa (210 to 300 psi)	105 to 210 kPa (15 to 30 psi)

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   (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.

Indications from the Compressor Pressures

Use Table 2 in order to diagnose indications from the pressures.

Refrigerant Circuit Problems

System Condition 1

1. Low-pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

2. High-pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

   Note: Ambient temperature is above 21° C (70° F).

3. Bubbles continuously appear in the sight glass.

Probable Cause

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

1. Perform a leak test. Refer to Testing and Adjusting, "Refrigerant Leakage - Test".

2. If leaks are found, recover the refrigerant. Refer to Testing and Adjusting, "Refrigerant Recovery".

3. Repair leaks.

4. Checking the compressor for loss of oil is important if a large amount of refrigerant was lost.

5. Perform a partial charge of the system.

6. Evacuate the system. Refer to Testing and Adjusting, "Refrigerant System - Evacuate".

7. Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to Testing and Adjusting, "Refrigerant System - Charge".

8. After the system is charged and operated for a minimum of 10 minutes, perform a performance check. Refer to Testing and Adjusting, "Air Conditioning Performance - Test".

System Condition 2

1. Low-pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

2. High-pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

   Note: Ambient temperature is above 21° C (70° F).

3. When the air conditioner is operated at maximum cooling, the cooling performance is insufficient.

4. 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

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

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

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

1. If the expansion valve inlet is cool to the touch, perform the following procedure:

   • Set the air conditioner temperature control switch to the maximum COOL position and set 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 Testing and Adjusting, "Refrigerant Recovery".

   • Replace the expansion valve. Refer to Service Manual, SENR5664, "Expansion Valve - (Air Conditioner) Remove and Install" section in Disassembly and Assembly.

   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 Testing and Adjusting, "Refrigerant System - Evacuate".

   • Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to Testing and Adjusting, "Refrigerant System - Charge".

   • After the system is charged and operated for a minimum of 10 minutes, perform a performance check. Refer to Testing and Adjusting, "Air Conditioning Performance - Test".

2. 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. Refer to Testing and Adjusting, "Air Conditioning Performance - Test".

3. Replace the refrigerant receiver-dryer.

   • Evacuate the system. Refer to Testing and Adjusting, "Refrigerant System - Evacuate".

   • Charge the system with the correct amount of refrigerant. Measure the refrigerant by weight. Refer to Testing and Adjusting, "Refrigerant System - Charge".

   • After the system is charged and operated for a minimum of 10 minutes, perform a performance check. Refer to Testing and Adjusting, "Air Conditioning Performance - Test".

System Condition 3

1. Low-pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

2. High-pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

   Note: Ambient temperature is above 21° C (70° F).

3. The cylinder section of the refrigerant compressor gets excessively hot.

Probable Cause

Worn piston rings causing blow-by of gases around the rings will result in inefficient compressor operation. Replace the refrigerant compressor.

1. Remove the refrigerant charge. Refer to Testing and Adjusting, "Refrigerant Recovery".

2. Evacuate the system. Refer to Testing and Adjusting, "Refrigerant System - Evacuate".

3. Charge the system. Refer to Testing and Adjusting, "Refrigerant System - Charge".

4. For the oil level in the system, refer to Testing and Adjusting, "Refrigerant Compressor Oil - Check".

System Condition 4

1. Low-pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

2. High-pressure gauge reading is normal. For normal operating pressures, refer to Table 1.

   Note: Ambient temperature is above 21° C (70° F).

3. Bubbles continuously appear in the sight glass.

4. The cylinder section of the compressor does not get hot.

Probable Cause

The expansion valve could be held in the OPEN position.

1. Replace the expansion valve. Refer to Service Manual, SENR5664, "Expansion Valve - (Air Conditioner) Remove and Install" section in Disassembly and Assembly.

System Condition 5

1. Low-pressure gauge reading is normal. For normal operating pressures, refer to Table 1.

2. High-pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

   Note: Ambient temperature is above 21° C (70° F).

3. Bubbles continuously appear in the sight glass.

Probable Cause

The condenser is dirty or clogged.

1. Clean the condenser.

System Condition 6

1. Low-pressure gauge reading is normal. For normal operating pressures, refer to Table 1.

2. High-pressure gauge reading is below normal. For normal operating pressures, refer to Table 1.

   Note: Ambient temperature is above 21° C (70° F).

3. High pressure lowers gradually.

Probable Cause

The high-pressure circuit before the receiver-dryer is clogged.

1. Remove the clog or replace the part.

Blower Motor Does Not Rotate

Note: If any abnormal condition is evident such as, blower motor does not turn due to interference of fan and case, or the blower motor is seized, etc., remove the cause first, such as to remove the interference, and then connect power to the power terminal of the blower motor in order to see if the motor rotates first.

Note: All connectors disconnected for testing should be reconnected after the making repairs.

1. Use the fan switch to set the air flow to the maximum High position.

2. Remove connector (G) from the blower motor connector. Check to see if voltage is applied between the "PK" wire and the "BK/WH" wire on connector (G). If there is no voltage, see Step 3. If there is voltage, then the blower motor has failed. Replace the blower motor.

3. Check the battery voltage applied between the "PK" wire at (+) side of the blower motor and shovel body. If there is no voltage, see Step 3. If there is voltage, see Step 7.

4. Check the blower motor relay. Directly connect the "WH/RD" wire and the "PK" wire on the blower motor relay to see if the motor retates. If the blower motor does not rotate, the wire harness is defective. Check and repair the wire harness or replace the wire harness. If the blower motor rotates, see Step 5.

5. Check to see if battery voltage is applied between the "WH/RD" wire of the blower motor relay and the shovel body. If there is no battery voltage, check and repair the wire harness or replace the wire harness. If there is voltage, see Step 6.

6. Ground the "BR" wire of the blower motor to see if the blower motor rotates. If the blower motor does not rotate, replace the blower motor relay. If the blower motor rotates, check and repair the wire harness or replace the control panel.

7. Check to see if there is voltage between the "YL" wire and the "BK" wire on the fan control. If there is no voltage, replace the control panel. If there is voltage, see Step 8.

8. Remove and check the fan control. Refer to "Specifications". If the fan control checks out normal, check and repair the harness. If the fan control is faulty, remove the cause of the problem and replace the fan control.

Specifications

Illustration 4	g02570436
Fan Control

Blower motor voltage (reference value) for each preset air amount at shovel ACC voltage 27 V.

Lo ... 10 V

Mi ... 14 V

M2 ... 17.3 V

M3 ... 20.5 V

M4 ... 23.8 V

Hi ... 27 V