Sensors on '99 2500 5.7L AC

The truck is a '99 2500 Chevy pickup w/ 5.7L and AC. The AC compressor stops working at will, but when working is producing cold air. The problem is intermittent as one time it will work fine for miles and others it stops cooling within a short distance, not necessarily completely up to temp, and running the compressor. The person has not tried stopping the engine for a few seconds and restarting to see if this resets the sensors, etc.

My question is what are the two sensors sensing on the AC system, one going into the compressor on the top (HOT Side) and one going into the silver canister on the firewall (COLD Side). If one of these is on the fritz will it stop the compressor? What do they sense? Can they be replaced without discharging the system?

Thanks, Kevin

Reply to
Kevin
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Kevin,

Hot side is high-pressure cut-off switch, cold side is low-pressure cut-off switch. Both will kill the compressor if they're acting flaky. They're plumbed right in AFAIK, hence the system needs to be evacuated then refilled to replace.

Doc

Reply to
"Doc"

First you need to make sure that your AC system has the proper pressures and amount of R134A refrigerant. This can cause cycling of the compressor without anything being wrong with your switches.

You could try adding one can of R134A, but it would be better to check the pressure with a gauge set first.

The symptoms you describe could be a low refrigerant level, which means you may have a small leak in your system.

Reply to
Hardpan

The AC pumps out very cold air when it works and when it does work, it usually works fine. Every so often though it will start out working and then drop off completely, no compressor action. It's not doing the engage and disengage routine of low refrigerant character. I'm sure he will have the pressure checked first and then look into having the sensors replaced. They have 135K miles on them, not the engine though. A "mechanic" told him the engine lost a cylinder or two and told him it required a rebuilt engine be dropped in it. Imagine the surprise when he had to replace a fuel injector because the rebuild was running the same way the original engine was running!!!! Imagine that exchange of words!!! A report on the torn down engine showed nothing wrong and little wear on parts. At least the engine will not need to be worried about for another 100K+. :-)

Price of a rebuilt eng>

Reply to
Kevin

This was fixed today as the person that owns the truck drove it until it acted up and then went straight to the mechanic's shop. The low cutoff sensor was the culprit, sensor on the canister by the firewall. It was replaced in a matter of minutes and now runs good and cold without issues. The system did not have to be evacuated to replace that sensor.

Thanks again for the input from those that offered it.

Reply to
Kevin

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