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New a/c compressor need help!

stallonepanerai on Sun May 17, 2015 9:50 PM User is offline

Year: 1999
Make: chevy van
Model: 3500 express van
Engine Size: 5.7 8 cy
Refrigerant Type: R134A
Country of Origin: United States

Hey Guys!

Im trying to help a friend with his van. The a/c compressor is shot. I went to the local auto parts store to pick up a new one with a new drier. I didnt notice until after I added oil and mounted the pump it was missing something the old one had. The old oem pump had a 2 prong plug on the butt end of the compressor. The new one doesnt. Also both the new and old compressor have a 2 prong plug right behind the belt pulley. I created a vacuum on the system then I started to add a can of 134a. It sucked it all in but the pump clutch didnt engage. So I added another and still nothing. So then I realized the 2 prong plug on the butt end of the compressor wasnt there. So I had to jump the wire since I had no place to plug it in anymore. Once I did that the a/c clutch engaged and works fine. So then I added the last can of refrigerant. My question is can I leave the pump jumped all the time since thats the only way it will run? The pump clutch will only shut off when the van is turned off or when the a/c switch on the dashboard is off or not on a/c. Will the pump get damaged if it runs all the time when the a/c is on and not cycling?

Thanks in advance!!!

mk378 on Mon May 18, 2015 9:04 AM User is offline

Cycling is controlled by the switch on the accumulator, when the low side goes below about 25 it should cycle off. At idle in hot weather there may be no cycling, this will not hurt anything. Make sure you are using the specified amount of refrigerant, and keep an eye on the high side. Excessive high sides (usually because the engine-driven fan clutch is worn out) will cause poor performance.

The switch on the back end of the compressor is a high pressure cutoff to prevent damage in case of abnormally high pressure (high side > 450). You are supposed to remove the switch from the old compressor and use it to replace the blank plug that comes with a new compressor. This can only be done with the system empty of refrigerant.

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