A/C compressor

[Cowboy476]

I have a 2011 Silverado 1500 with the 5.3L V8. The a/c compressor just quit out of nowhere and I bought a scan tool that allows me to turn the A/C relay command On/Off. When I turn it on the compressor kicks in and it blows nice cold air but I have to leave the scan tool hooked up the entire time. I have not physically gotten the pressure readings off the system but my scan tool says the A/C high side pressure sensor reads 2.69 V and 1708 kPa. Is there anything I can change that will allow the A/C to work when I hit the button in the cab? The compressor is quiet and kicks on and off perfectly if I have it hooked to my scan tool. I just don't want to jump to conclusions and change out a compressor that works perfectly fine. So could the high side pressure sensor be bad? I know I will get the physical pressures hopefully tomorrow. Thanks in advance.

[CamGTP]

1700kpa is nearly 250psi, that could be the high pressure cut off point to turn the compressor off.

 

Usually you only want to see 200-220psi on the high side.

[Cowboy476]

So would you say there is restriction in the system somewhere or is the system possibility just over pressured. Which it being over pressured would be strange because it's always been cold air and I have had no reason to add to it. 

[CamGTP]

Or the pressure sensor is bad itself.

[Cowboy476]

High and low side both reading as pictured. Compressor will not engage, switched relay and checked fuse but still nothing. Yesterday I was able to engage the system with a scan tool but its not working today for some reason.

[Cowboy476]

Ok so I finally got the A/C system to turn on. Reason it wouldn't turn on was operator error on my part. Anyways I hooked up the pressure guages and they read as follows in the pictures. The system ran extremely cold for 40 minutes or so before the accumulator started to freeze over and moisture fog started coming out of the vents. Once the moisture fog started coming out I started losing all air flow from the vents. I let the system continue to run an additional 15 minutes or so while sitting in the driveway and the accumulator eventually thawed out and while it was blowing cold air it wasn't full blast maybe 50% or so. It never regained full blower speed but the air was cold but you can hear that it's either still frozen inside the accumulator or there is another issue. At this point I can turn the system off for 5 minutes or so and restart it and it's back to blowing ice cold air at full speed. The included pictures show the guage pressure when the accumulator was froze over and as the accumulator unthawed itself the low side pressure began to rise. There was no drastic change in pressure at all during the time I monitored the system. What I mean by that is the low side never spiked high or low when the compressor was running and the high side stayed pretty consistent as well. Now with me forcing the A/C system to run would the compressor cycle on and off as normal or would it just run at 1 constant speed? That is the only thing I forgot to pay attention too. So the pictures are accumulator frozen and low side guage reading hardly anything and the high side maybe 125. As the system unthawed itself both low and high side pressures started to rise but very slowly. Also the pressure switch was still reading 1.16 V. The picture of the accumulator frozen would not upload due to size but the guages did upload. 

[txab]

If you've over ridden the low pressure cut out switch, then compressor will run forever and continue to freeze. That's why you're experiencing icing at the evap. Have you replace the low pressure and high pressure switch or at least tested them

Edited August 21, 2023 by txab

[Cowboy476]

I have not yet tested the A/C pressure switch which I am told is located above or on the compressor itself. Somewhere in that general location. The system does not have low pressure or high pressure side switch like normal only the 1 pressure switch located at the compressor. Honestly if I'm going to dig off into the system and fight to get it out and back in I will probably just replace the sensor. Question is will this require a system evac or am I lucky enough to be able to change it without evacing the system. Thanks for your reply

[txab]

Usually there is a schrader valve on the port. So you won't lose charge.

Are you sure it's on the compressor and not on the low pressure line somewhere?

Do some exploration

Edited August 22, 2023 by txab

[Cowboy476]

From what I understand the sensor is right above the compressor on the high side I assume but I will look around. I know its not on the low side anywhere. 

Edited August 22, 2023 by Cowboy476
Wrong information

[txab]

Shows there is a low pressure switch available

[Cowboy476]

I will definitely look and let you know. 

[Cowboy476]

Honestly I looked the system over and I only found 1 switch right before the compressor and can be seen by looking through the wheel well. Any help on possibly locating a second switch would be helpful. Just trying to get everything in place so everything can be replaced at once.

[SmokChsr]

Actually those pressures, and the fact that it's freezing over would be an indication that it's low on Freon, or the line filter is clogged. But mostly very low on gas.  

[Cowboy476]

This is the only sensor I see and is the thing beside it the inline filter or are you referring to something else?