Chevrolet Silverado 1500 / 2500 / 3500:

2002 Silverado A/c clutch won't engage | Page 2

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# 11  2/13/2012 9:35 PM

New member
Registered: 2/3/2012
Posts: 6

Re: 2002 Silverado A/c clutch won't engage

TechHelp2 wrote:

If you can get the truck to someone who has a scanner to see if they can tell you if there are any trouble codes stored in the computer. They can also check if the PCM is giving the ground signal and if other sensors are working properly. If you don't then I have given you some other things to look at to see if we didn't overlook anything.

If you don't have anyone then go to your local Auto Zone auto parts store and they will be able to scan the computer for any codes and they usually do it for free. 

Is it cold where you are? Is you’re A/C system automatic or manual?

The list below is for an automatic system with the use of a factory scanner.

If the PCM doesn't receive a signal from the A/C control module the clutch will not engage.

The A/C compressor clutch will not engage if temperature outside is below 38 degrees.

The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F).

The engine coolant indicator will illuminate at this temperature.

These actions will enable the A/C compressor to operate.

If the HVAC control module does not respond to requests, the module is inoperative.

This action ensures that the power train control module (PCM) is getting an A/C request from the HVAC control module.

If the A/C request LED does not illuminate the HVAC control module is not grounding the A/C request signal circuit.

Since the A/C system pressure has been verified in Step 4 this step will verify the integrity of the A/C request signal circuits, if the A/C Request Signal parameter is Yes then there is a concern with the A/C high pressure switch.

Since the A/C system pressure has been verified in Step 4 this step will verify the integrity of the A/C low pressure signal circuit and the ground circuit of the A/C low pressure switch, if the A/C Compressor Cycling Switch parameter is Normal then there is a concern with the A/C low pressure switch.

If the test lamp remains illuminated the A/C compressor clutch relay control circuit is shorted to ground.

If the fused jumper opens during this step the A/C compressor clutch supply voltage circuit is short to ground.

Ensure that both A/C request signal circuits of the A/C high pressure switch are tested for listed conditions.

Take a look at these suggestions and let me know how you make out.

I actually have an OBDII scanner, but its just a basic one. It reads "Pass, no codes returned" when I scan the truck. I'm sure it can't read any real time data. It's this basic model.

I'm pretty sure I have manual A/C controls. I have to turn the A/C heater on myself. I don't think anything happens auto. 

This is what my control unit looks like.

It does get a little cold here at night, in the 30's F. But it usually stays up around 50 or 60 during the days.



# 12  2/14/2012 3:30 AM

Registered: 11/24/2009
Posts: 1301

Re: 2002 Silverado A/c clutch won't engage

The basic scanner you have only reads OBD2 codes; it won't read body computer codes.

If you look at your scanner does it have any of the A/C switches like the low pressure switch and the high pressure switch?

It may just say A/C on or off. With the engine running and you turn the A/C on does the status of the A/C change either on or off or yes or no? This will help you in telling if the body computer is switching on or off.

When you put the A/C on do the cooling fans turn on? If they do not turn on then one of the input switches or sensors are not working.

Retrace your steps when you took the compressor off the engine, did you remove any ground wires or unplug any sensors? There must be something missing we just are not seeing.

Do one more test, disconnect both battery cables and put them together, turn the key on with the two cables touching; this will discharge any capacitors in the system and may reset the modules. It probably won't work but it is worth the try.

Try these suggestions and get back to me when you can. I will keep looking for other solutions.
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