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TXV Air Conditioning (A/C) System Diagnosis (Insufficient Cooling)

TXV Air Conditioning (A/C) System Diagnosis (Insufficient Cooling)

Step Action Yes No
IMPORTANT: Some conditions which are normal to correct air conditioning (A/C) system is operation may lead an owner to wrongly suspect a problem exists.
Under conditions of high humidity, the air discharged from the A/C system may not feel as cold as expected. This is because the vaporized moisture in humid air heats more effectively than does dry air, making the humid air much harder to cool.
In terms of overall comfort, however, the dryer, dehumidified air coming from the A/C system during hot, humid weather, evaporates more moisture on a person's skin and provides more of a cooling effect than air which is cooler but more humid.
This fact should be explained to an owner if a mechanical cause for a persistent complaint of insufficient cooling cannot be found. Refer to Symptoms - HVAC Systems - Manual .
1
  1. Inspect the compressor clutch wire connector for an open or poor connection. Refer to HVAC Compressor Clutch Does Not Engage and/or Testing for Intermittent Conditions and Poor Connections .
  2. Inspect the following fuses:
    • The A/C
    • The HTR
    • The IG
    • The DEF
    • The Blower
Did you find and correct the condition?		 Go to Step 18  Go to Step 2 
2
  1. Inspect the temperature control and cable operation.
  2. Move the temperature control lever from the coldest to the hottest positions.
  3. Listen for the door hitting at each end.
  4. Repair as necessary. Refer to Temperature Control Cable Adjustment in HVAC Systems - Manual.
Did you find and correct the condition?		 Go to Step 18  Go to Step 3 
3 Inspect the blower motor for proper operation. The blower motor speed should increase at each speed level as the switch is turned towards HIGH and then decrease as the switch is turned towards LOW.
Did you find and correct the condition?		 Go to Step 18  Go to Step 4 
4 Inspect for a loose, damaged, slipping or missing compressor drive belt. Refer to Drive Belt Replacement in Engine Mechanical-1.8L (LV6) or Drive Belt Replacement in Engine Mechanical-1.8L (LNK).
Did you find and correct the condition?		 Go to Step 18  Go to Step 5 
5 Inspect the condenser fan for correct operation. Refer to Cooling Fan Inoperative (Inoperative in Low Speed) or Cooling Fan Inoperative (Inoperative in High and Low Speeds) or Cooling Fan Inoperative (Inoperative in High Speed) or Cooling Fan Inoperative (Low Speed Operates in High Speed) in Engine Cooling.
Did you find and correct the condition?		 Go to Step 18  Go to Step 6 
6
  1. Inspect the condenser for a restriction in airflow.
  2. Clean and/or repair the condenser as necessary. Refer to Condenser Replacement .
Did you find and correct the condition?		 Go to Step 18  Go to Step 7 
7
  1. Inspect the compressor for seizure.
  2. Stop the engine.
  3. Disengage the compressor clutch.
  4. Rotate the compressor clutch plate, not the pulley, by hand.
Does the compressor clutch plate turn freely by hand?		 Go to Step 8  Go to Compressor Replacement 
8
  1. The ambient air temperature must be at least 16°C (60°F).
  2. Connect the pressure gages of a properly calibrated J 39183-C  R-134a manifold gage set to the High and Low side service ports on the vehicle. See Special Tools .
  3. Both the High and Low side pressures should be almost equal to each other.
Are the High and the Low side pressures 345 kPa (50 psi) or higher?		 Go to Step 9  Go to Step 13 
9
  1. Start the engine and run at idle.
  2. Set the blower speed to the highest position.
  3. Set the temperature control to the coldest position.
  4. Set the mode control to the I/P outlet position.
  5. Press the A/C switch to the ON position.
Does the compressor clutch engage?		 Go to Step 10  Go to HVAC Compressor Clutch Does Not Engage
10
  1. Monitor the compressor for any unusual knocking or loud moaning noises and/or compressor drive belt slipping.
  2. Cycle the compressor clutch by pressing the A/C switch to the OFF position and back to the ON position.
  3. Notice if the compressor drive belt is slipping.
Is there excessive compressor noise?		 Go to Compressor Replacement  Go to Step 11 
11
  1. Visually inspect the lines for a frost spot indicating a restriction.
  2. Feel the lines for an abrupt temperature change. The high side components should feel warm/hot from the compressor outlet to the expansion valve.
  3. The low side components should feel cool/cold from the evaporator outlet to the compressor inlet.
  4. Repair as necessary.
Did you find and correct the condition?		 Go to Step 18  Go to Step 12 
12 Feel the evaporator inlet pipe (the small pipe) and the evaporator outlet pipe at the bulkhead. The evaporator inlet pipe should feel warm to the touch. The evaporator outlet pipe should feel cool to the touch.
Does the evaporator inlet pipe feel colder than the evaporator outlet pipe?		 Go to Step 13  Go to Step 15 
13
  1. Leak test the refrigeration system. Refer to Leak Testing .
  2. Add 0.45 kg (1 lb) of the refrigerant as necessary.
  3. Evacuate and recharge the system. Refer to Refrigerant Recovery and Recharging .
Is a leak present?		 Go to Step 14  Go to Step 16 
14 Repair the leak. Refer to Leak Testing  and Refrigerant Recovery and Recharging .
Is the repair complete?		 Go to Step 18  -
15
  1. Run the compressor.
  2. Monitor the clutch operation and the system pressures for 5 minutes.
  3. The compressor should disengage when the system pressure is outside the specified values.

    High Side Pressure Range:  1275-1670 kPa (185-244 psi)

    Low Side Pressure Range:  150-300 kPa (21-43 psi)

Does the compressor stay engaged outside the specified values?		 Go to Step 17  Go to Step 16 
16
  1. Discharge the system.
  2. Inspect for a restricted or malfunctioning expansion valve. Refer to Thermal Expansion Valve Replacement .
Is the repair complete?		 Go to Step 18  -
17 Replace the A/C refrigerant pressure switch. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement .
Is the repair complete?		 Go to Step 18  -
18 Operate the system in order to verify the repair. Refer to Air Conditioning (A/C) System Performance Test .
Did you correct the condition?		 System OK Go to Step 1 
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