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AC clutch

lwflyer on Mon April 12, 2010 12:54 AM User is offline

Year: 2001
Make: GMC
Model: Topkick
Engine Size: 8.1
Refrigerant Type: 134a
Pressure Low: 90
Pressure High: 0
Country of Origin: United States

My AC is not getting cold. I checked my low side reading and it is at 90. My clutch on the compressor is not engaging. I check the wires and I have 13 volts and I also ohm'd the wires and have 3 to 4 ohms so I'm fairly sure the coil is ok.
I'm not sure of what else I can check.
Any suggestions would be greatly appreciated.

GM Tech on Mon April 12, 2010 9:16 AM User is offline

Tap on clutch with hammer handle- see if it pulls in-- if so, your air gap is too wide- it can be narrowed- depending on your compressor brand.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Cussboy on Mon April 12, 2010 9:32 AM User is offline

Quote
Originally posted by: GM Tech
Tap on clutch with hammer handle- see if it pulls in-- if so, your air gap is too wide- it can be narrowed- depending on your compressor brand.

With engine running and AC switched on, Tap on clutch CAREFULLY with hammer handle- see if it pulls in

lwflyer on Tue April 13, 2010 5:00 PM User is offline

Tried the end of the hammer still no clutch. I tried adding 134a and now read 90psig on the low side and 70psig on the high side.
What else can I try or look for?

Thanks

mk378 on Tue April 13, 2010 10:48 PM User is offline

Did you measure voltage between the wires at the coil? If not do that, also check that the other wire of the clutch is grounded. You could have power on one wire but no ground.

If you really have battery voltage between the two wires, it should pull in. You can jump it direct to a battery with the engine off then push on the plate with your hand (engine off remember).

lwflyer on Tue April 13, 2010 11:08 PM User is offline

Thank you. I will double check tomorrow. I tested voltage with the two wires and it was 13 volts. I thought I checked the - side to ground but I will check it again.
I also checked the coil ohms and it was around 3.

lwflyer on Wed April 14, 2010 10:26 PM User is offline

Could a blocked orifice cause the low side pressure to be high and the high side pressure to be lower or is it because my clutch is no engaging?

Thanks

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