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2004 GM 2500HD Low Pressure Cutoff Switch

diverdon on Mon May 07, 2012 1:53 PM User is offline

Year: 2004
Make: Chevy
Model: 2500HD
Engine Size: v-8
Refrigerant Type: 134a
Ambient Temp: NA
Pressure Low: NA
Pressure High: NA
Country of Origin: United States

2004 GM 2500HD Truck
Hello, I'm trying to help a friend get his A/ac going on a truck his son owns .. The Compressor has stopped coming on recently . I had thought the switch at the Accumalator was the Low/High and CCOT cycle switch however when I jumped this switch the compressor still won't engage..

I realize there could be several reasons for the compressor to not kick in but wanted to try this first . I installed my manifold gages on the service ports and there is some Refrigerant in the system . High side was reading 170lbs even with the compressor turned off ..

My real question is that there is another switch on the back side of the compressor or one of the fittings going to it . This compressor is on the bottom of the engine and the truck has tall tires making access a little tough for an old fart like me . Can someone tell me if this is a low pressure cutoff switch or not before I start climbing in the engine bay to get to it ?

Thanks in advance for any help I can get .. Don J.

mk378 on Mon May 07, 2012 4:51 PM User is offline

The switch on the back of the compressor is a high pressure cutoff that trips around 450 psi.

Check if the clutch coil is getting voltage. It could be a bad clutch or the gap is too large. If you're not getting voltage, check the compressor fuse and relay.

With the engine off and cold, static pressure should correspond to the ambient temperature (read the R-134a temperature scale on the inside of the gauge.) If significantly higher than that, the refrigerant charge could be contaminated with air.

Edited: Mon May 07, 2012 at 4:52 PM by mk378

diverdon on Tue May 08, 2012 12:27 PM User is offline

Thank You for the reply ..You have saved me some time and hassle of crawling into that engine compartment .. Never thought of the clutch maybe being bad . I should have maybe as that was what broke on my car first ... Honda Element.. I changed it myself . All day job for me but I saved $400 in labor ..

I will check to see if the clutch is getting power first . Then the fuse and relay "If" the clutch isn't getting power .. I found the relay in a box under the hood on the left side inner fender well. and there was a fuse right next to it marked ... (AC) .. Think that's the clutch fuse ????

Thanks again for the help .. This truck belongs to a friend of mine I work with and he wants to give it to his son .. It would be nice if the A/C worked ...

Thanks soooo much , Don J.

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