Eric Pack

Have a 2010 Silverado LS 4.8

Having a weird a/c issue I cant figure out. A/C will blow cold for a short period of time the compressor will then proceed to cycle on and off intermittently for random amounts of time. My high and low side pressures are good several days in a row no signs of a leak. Mechanic thought perhaps the refrigerant temp sensor was bad. Not wanting to pay 1k for labor I proceeded to drop the dash and replaced the temp sensor but the same problem persists.

Heres the deal, with the temp sensor disconnected entirely the a/c runs cold and consistently although I realize this will cause the compressor to run continuously unless I turn the ac off. What am i missing? This model does not have digital climate control so I dont think there is a cabin temp sensor

oilcanhenry

Does your Silverado have an ambient temperature sensor on the front of the condenser?

jaredjeandron

I have this exact same problem happening right now, pressures are good but compressor keeps cutting in and out. I have the LS 2010 1500 with manual temp controls, could it still be a temp sensor in mine? I’m about to drive myself mad trying to figure it out on my own.

KChevy75

How often is it turning on and off? It's normal for the compressor to cycle on and off unless it's doing so relatively quickly. While watching your low side gauge, when the compressor cycles on, does the pressure drop a lot? If so you're low on refrigerant.

Has anyone ever worked on your A/C in the past? Was it ever low on refrigerant and was topped off at some point? If so, they may be a lot of air in the system. I'll need to be reclaimed, the leak found and repaired then a vacuum pulled and the system charged.

jaredjeandron

So far the system I have is stock from the manufacturer (2010 Silverado 1500 LS 4.8L). I’ve never had work done on it and I’m an hvac tech so once I noticed the a/c cutting in and out I went back to my shop and used some low loss fittings and hooked up my gauges. So what it does is the clutch on the compressor kicks in and it runs nice and cold out of the vents with 36 psi at 38 degrees on the low side and 185 psi at 125 degrees on the high side on a 94 degree day with 40% humidity. So the pressures are in range but the clutch engages and disengages every 5-10 seconds. Sometimes in park the compressor will run and sometimes not at all. On the drive to pick up my kid I was worried about the heat in the truck because it was cutting in and out but the whole drive back it ran 100%.

My guess is either the pressure switch or the refrigerant temp control switch but I’m hoping it’s the former so I don’t have to pull the dash.

KChevy75

It's hard to go by pressure as all systems are different but it seems to me like you are low on refrigerant. With an ambient air temperature of 94F, I'd think you'd want to be around 50 psi on the low side. The only real way to know for sure that your charge is correct is to recover the refrigerant, pull a vacuum and recharge it with how many lbs shown on the label under the hood. I think the silverado is 1.6 lbs.

oilcanhenry

The issue is that you ARE an HVAC tech, not an automotive A/C tech, I'd wager.

Cars and light or heavy vehicles are not home A/C systems at all. If that were the case, I'd be rolling in money right now. All kinds of things can cause a vehicle's A/C compressor to stop and start. All I care about is that my vehicle A/C is putting out 38-41 degrees F at the vents. I have had vehicles that cycled the compressor, but as long as the air was _cold_, I could care less. You know what they say about not fixing something that is not broken?

My vehicles put out 38-41 F degrees temp or I will find out why they do not. So far with my 2015 Chevy Malibu, I am very happy with it and I have not had to do anything but add a small amount of R-134A in my 21 year old Chevy K-1500 4x4 pickup truck as well as leak detector, in case it ever has a real leak, not just a small amount of R-134A which is normal usage in an older vehicle.

Both of my Chevrolet vehicles air-conditioning systems work just fine. I am quite old enough to recall the old R-12 "Freon" A/C systems quite easily and I am an expert in automotive air-conditioning systems.

Breadedturnip

Did you ever figure out what the problem was?

jaredjeandron

yeah the evaporator coil temp sensor was malfunctioning and reading 130-190 degrees on a 40 degree coil. I had a local shop run diagnostics to find that out, paid them for the diag. and ordered a new sensor. I only had to pull the glove boxes and used a firm wire to fish tape the new sensors wires but it was an easy swap and fixed the issue. Of course I had issues this summer as well but ended up being about 3/4lbs low on refrigerant.

Breadedturnip

Hmmmmm I know I do have evap air temperature sensor reading -9 and some duct Temp sensors reading-51. Do you happen to have a picture of the sensor and its location or a part number?

Thanks for the reply