Automotive Air Conditioning Information Forum (Archives)

reedaerospace on Thu September 11, 2008 11:07 PM

Year: 1991
Make: chevrolet
Model: 1/2 ton truck
Engine Size: 350
Refrigerant Type: convert 134a
Country of Origin: United States

HI all

I have a 1991 chevy truck and the ac light on the control panel flashes and the comp wont engage. I have converted this system to 134a used a variable orifice valve . It cools great hotwiring the clutch. I put a jumper in the lo-psi switch and it still wont come on. Does any one have any ideas or maybe a wiring diagram.

Thanks Kendall

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Kendall

GM Tech on Thu September 11, 2008 11:17 PM

You've set a code in the control head- '91 and '92 C/K trucks have this feature (a/c lite flashes for 2 min on each ignition on)-- you are either low on refrigerant (most likely scenario) or you need to enact the TSB for false code tripping- in the technical pages here-- The code sets by counting compressor cycles- and it is trying to save your compressor from burning up inside because it is running very low on refrigerant- look at your shaft seal on front of compressor- is there oil slinging on the hoodliner? on the radiator hose? is front of clutch wet?

You can reset the code by unhooking battery for 10 seconds-- but it will soon disable itself again if you take no action

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

reedaerospace on Fri September 12, 2008 1:27 AM

I just bought a rechargeable uv light from matco tools that you could kill a vampire with and everything looks ok so far for leaks. I will try resetting the control head. and check out that tsb.

Thanks Kendall

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Kendall

iceman2555 on Fri September 12, 2008 3:20 PM

First...gotta determine if the system is fully charged....with this retro....got a funny feeling...esp with the variable orifice.....its a bit undercharged.....

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

Chick on Fri September 12, 2008 9:53 PM

Did you pull a vacuum and charge into the vacuum? You do have to reset the control head, and follow the advice given, but since you didn't state how you retrofitted it, I have to ask...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

reedaerospace on Tue September 16, 2008 1:04 AM

I reset the control head and everything is working great. After I flushed the system and changed the compressor oil,added dye and vacummed I charged it to the origional recommended charge of the old r-12 . I figured since you use lass 134a and more with the VOV I would start there. The vent temp was 38 degrees. I am going to check for leaks again this weekend . I am a heavy truck mechanic (21 Dealership years Peterbilt,International,Volvo,Ford/Sterling and currantly Freightliner) and do daily ac repairs at work. Thankyou for the help as I do not have much refrence material on the little stuff


Kendall

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Kendall