Heating, Ventilation and Air Conditioning: Diagnosis Chevrolet Silverado 2500

Diagnostic Starting Point - Heating, Ventilation & Air Conditioning

The Heating, Ventilation and Air Conditioning (HVAC) system is divided into three separate sections. The first, Heating, Ventilation and Air Conditioning, has all procedures that pertain to a HVAC component or function that is not specifically associated with an automatic or manual control system. The second, HVAC Systems - Manual, has all procedures specific to the manual control system. The third, HVAC Systems - Automatic, has all procedures specific to the automatic control system.

Begin the system diagnosis with the

1. «SYMPTOMS - HVAC SYSTEMS - MANUAL»(ref-175817-S14776921632005042700000) for a system without DTCs
2. «DIAGNOSTIC SYSTEM CHECK - HVAC SYSTEMS - AUTO»(ref-190277-S09288727582005091400000) for a system with DTCs

The Diagnostic System Check will provide the following information

1. The identification of the control module(s) which command the system.
2. The ability of the control module(s) to communicate through the serial data circuit.

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Review the Description and Operation information to help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the Description and Operation will also help you determine if the condition described by the customer is normal operation.

The HVAC Description and Operation information is divided into

1. «AIR DELIVERY DESCRIPTION & OPERATION»(ref-175817-S40237988352005042700000) in HVAC Systems - Manual
2. «AIR TEMPERATURE DESCRIPTION & OPERATION»(ref-175817-S06789944912005042700000) in HVAC Systems - Manual
3. «AIR DELIVERY DESCRIPTION & OPERATION»(ref-175920-S30187164942005042800000) in HVAC Systems - Automatic
4. «AIR TEMPERATURE DESCRIPTION & OPERATION»(ref-175920-S19276166432005042800000) in HVAC Systems - Automatic

The Air Delivery Description and Operation contains the following topics

1. Air Speed
2. Air Distribution

The Air temperature Description and Operation contains the following topics

1. Heater Mode
2. A/C Mode
3. A/C Cycle

Leak Testing

Tools Required

1. J 39400-A Halogen Leak Detector
2. J 41447 R-134A A/C Tracer Dye-Box of 24
3. J 41459 R-134A A/C Tracer Dye Injector
4. J 42220 Universal 12V Leak Detection Lamp
5. J 43872 Fluorescent Dye Cleaner

Refrigerant Leak Testing

Important: General Motors passenger cars are now manufactured with fluorescent dye installed in the A/C system.

The preferred method of leak testing is the use of fluorescent dye. J 41447 is the only dye approved by General Motors. Follow the Fluorescent Dye Injection procedure for vehicles that do not already contain the fluorescent dye.

Air Conditioning (A/C) System Performance Test

This test measures the operating efficiency of the A/C system under the following conditions

1. The current ambient air temperature
2. The current relative humidity
3. The high side pressure of the A/C system
4. The low side pressure of the A/C system
5. The temperature of the air being discharged into the passenger compartment

Compressor Leak Testing

Tools Required

Scheme 34

1. J 34992 Compressor Holding Fixture
2. J 39400-A Halogen Leak Detector
3. J 39893 Pressure Test Adapter
4. J 43600 ACR 2000 Air Conditioning Service Center

Bench-Check Procedure

1. Install the J 39893 on the rear head of the compressor.
2. Connect the J 43600 low side and high side lines to the corresponding fittings on the J 39893. The suction port (1) (low-side) of the compressor has a large internal opening. The discharge port (high-side) has a smaller internal opening into the compressor. The discharge port (2) (high-side) also has a deeper recess.
3. Use the J 39400-A in order to inspect for leaks at the following locations: The pressure relief valve (5) The rear head switch location The compressor front head seal The compressor rear head seal The center cylinder seal The through bolt head gaskets The compressor shaft seal
4. Perform the following steps if an external leak exists: 4.1. Perform the necessary corrective measures. 4.2. Inspect the components for leaks again in order to verify that the leak is corrected.
5. Recover the refrigerant.
6. Disconnect both hoses from the J 39893 .
7. Add 90 ml (3 fl oz) of new PAG lubricant to the compressor assembly.
8. Slowly rotate the complete compressor assembly (excluding the crankshaft and the drive plate hub) several turns in order to distribute oil to all of the cylinder and the piston areas.
9. Install a M9 x 1.25 threaded nut on the compressor crankshaft if the drive plate and clutch assembly are not installed.
10. Use a box-end wrench or socket and handle in order to rotate the compressor crankshaft or clutch drive plate on the crankshaft several turns. Performing the above action will ensure piston assembly to cylinder wall lubrication.
11. Using the J 43600, connect the J 39893 to the test plate high-side connector.
12. Using the J 43600, connect the charging station low-pressure line to the low-pressure port of the J 39893. Oil will drain out of the compressor suction port (1) if the compressor is positioned with the suction port downward.
13. Attach the compressor to the J 34992.
14. Mount the compressor in a vise in order to place the compressor in a horizontal position.
15. Use a wrench in order to rotate the compressor crankshaft or the drive plate hub ten complete revolutions at the speed of approximately one-revolution per second. Turning the compressor at less than one-revolution per second can result in a lower pump-up pressure. Low pump-up pressure may disqualify a good pumping compressor.
16. Observe the reading on the high-pressure gage at the completion of the tenth revolution of the compressor. The pressure reading for a good pumping compressor should measure 690 kPa (100 psi) or above. A pressure reading less than 620 kPa (90 psi) indicates one or more of the suction and/or discharge valves have an internal leak or an inoperative valve.
17. Perform the following procedure if one of the valves are leaking or inoperative: 17.1. Recover the refrigerant. 17.2. Disassemble the compressor. 17.3. Inspect the compressor for the cause of the leak. 17.4. Repair the compressor as necessary. 17.5. Reassemble the compressor. 17.6. Repeat the pump-up test. 17.7. Test for external leaks.
18. Recover the refrigerant from the high-side.
19. Remove the J 39893.
20. Tilt the compressor with the compressor suction port (1) and the discharge port (2) positioned downward.
21. Drain the PAG lubricant from the compressor. Allow the compressor to drain for 10 minutes.
22. Refill the compressor with the proper amount of PAG lubricant. Pour the PAG lubricant into the suction port (1).
23. If further assembly or processing is necessary, install a shipping plate or the J 39893. The shipping plate or the J 39893 prevents the following materials from entering the compressor until the compressor is installed: Air Dirt Moisture