2007 Chevy Uplander A/C Compressor

[gungfudan]

A friend of mine has a 2007 Chevy Uplander and the a/c was low on refrigerant. He filled it and it worked for a few days and it won’t kick back on. He jumped the relay and it comes on and still has good pressure. He has tried other relays and that are the same in the fuse box and none of them work.
What are we missing. I think he should buy a brand new relay and just try it.

any thoughts

 

[RonD]

I would keep the relay and change the vehicle it plugs into.....................................


AC works the same on most vehicles

Not sure what relay you are jumping???

The "freon" lines have pressure switches for "too low" and "too high" of pressure, these either pass 12volts or pass ground when they are closed(pressure is OK)
And these enable or disable the AC Compressor relay

In 2007 I would imagine the computer monitors the pressure switches and activates AC compressor relay accordingly
This also allows the computer to disable AC at wide open throttle, for max power

You can unplug a pressure switch and see if it is closed with an OHM Meter, 0 ohms is closed
If open then switch can be changed without draining the system, but it may be open because of a pressure problem


The "freon" is compressed by AC compressor, and goes into the High Pressure side of the system
It then goes to expansion valve when it is allow to expand into the evaporator in the heater box, this makes it very cold
And "freon" is now in the low pressure side and travels back to the AC Compressor

Too Cold is not good because lines can freeze up causing high pressure side to get too high or low pressure side to get too low, turning off relay/compressor until pressure equalizes

 

[gungfudan]

I would keep the relay and change the vehicle it plugs into.....................................

I wish he could. Chevys are notorious for electrical issues. I have owned 2 chevys a Lumina and a Colorado and they both had electrical issues. Not that I am saying this is an electrical issue.
Him and his wife are both bus drivers and they can't afford another vehicle. I am offshore or I would be there helping him with. I told him about the pressure switches before this post. I will let you know what he figures out.

 

[rusty ol ranger]

I wish he could. Chevys are notorious for electrical issues. I have owned 2 chevys a Lumina and a Colorado and they both had electrical issues. Not that I am saying this is an electrical issue.
Him and his wife are both bus drivers and they can't afford another vehicle. I am offshore or I would be there helping him with. I told him about the pressure switches before this post. I will let you know what he figures out.

I bought a colorado brand new in 08 and at 150 or 200 miles the oil pressure switch went out and shut the whole truck down.

 

[gungfudan]

So here is an update...
We can only find one pressure switch and it is three pronged. He ohmed it out with it off the line. I told him you have to do it with the vehicle on but it is hard to get, near impossible, a reading because of the location. I told him just change it out and see if that is it.

 

[07nhbpsi]

$20 says your friend overcharged the system.......the reason why it wouldn’t work a few days later? Ambient Temperature change......which changes the static pressure in system.....my advice is to vacuum the system out, and use the ‘proper tools ‘ to recharge the system....otherwise u cannot know exactly how much refrigerant is in system..