Need help - 3800 AC fix

Angus

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The car's ac hasn't worked for a bit and I'm trying to get remedy that. I like ac and being able to see where I'm driving when it's raining out...

So yesterday, I checked the Freon level and it was full. I also switched in a brand new ac clutch relay. Still not working.

I know I talked to Jeff @ goodfellas last night and I might try a different hvac headunit to see if it might be that.

Any other ideas of where to start?
 

Angus

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Is it blowing warm air, not blowing anything? Can you hear the compressor clutch kick in?

It's blowing warm air. I don't think I'm hearing the compressor clutch is kicking in...

I don't know if it's related, but the air direction or 'mode' won't change to anything different other than windshield and floor. You can set it to the vents or anything else, but it won't change...
 

Bru

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I'm dealing with a similar problem. The lack of vent modes is typical of a vacuum leak but I've also read of the vacuum block failing or getting clogged under the passenger side dashboard.

I visually inspected the line running from the inside to outside that controls vent functions but came up with zilch. I need to get a vacuum pump on there and see if it's leaking.

Sometimes battery acid spills and eats through the line. It runs under the hood near the battery on some models.
 

daturbosix

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Seriously though, see if you can find someone with a gauge so you can see how full or not full it is. Just push the little shrader valve quickly, see if there's pressure in there.
he had told me last night that he had a gauge on it. idk what kind of gauge. or gauges, but a refrigerant manifold would do no good right now because the compressor isnt cycling.

the comp. clutch DOES NOT CYCLE. even tried tripping the low/high switch with no results back when the car was still at my shop.
 

bikrboy128

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i've fixed a number of w-bodies that had this issue. the AC request signal wire (from the control head to the PCM) corrodes, usually near the accumulator/dryer. i believe it's a dark green wire, and it's in the harness that runs under the dryer. the ac pressure switch wires should lead into it.

have you checked for power and ground at the relay? also, check the HVAC vac feed line (runs up the passenger side strut tower). i bet there's a hole in it, which would explain why the mode doors arent working.
 

Turbocharged400sbc

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i've fixed a number of w-bodies that had this issue. the AC request signal wire (from the control head to the PCM) corrodes, usually near the accumulator/dryer. i believe it's a dark green wire, and it's in the harness that runs under the dryer. the ac pressure switch wires should lead into it.

have you checked for power and ground at the relay? also, check the HVAC vac feed line (runs up the passenger side strut tower). i bet there's a hole in it, which would explain why the mode doors arent working.

yeah ive seen that too as well as a shot electromagnet (seen em open and shorted...short will blow the fuse.
hook up a tech2 or snapon scanner and you can check for the ac request signal and comand ac clutch relay activation to do voltage testing to find where the problem lies
 

02BlueGT

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yeah ive seen that too as well as a shot electromagnet (seen em open and shorted...short will blow the fuse.
hook up a tech2 or snapon scanner and you can check for the ac request signal and comand ac clutch relay activation to do voltage testing to find where the problem lies

IIRC the HP tuners scanner can force ac clutch engagement...
 

Angus

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Had to go to the chevy dealership in Naperville for something else so I was talking to a tech about it and he hooked up his scanner to it. IIRC he said that the signal from the headunit was commanding the compressor to run but it wasn't running. He also noticed that my IAT (or C?) was reading -38* F and that could cause the ac not to run then.

I haven't looked at anything else, but does that sound legit? :dunno:
 
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