Automotive Air Conditioning Information Forum (Archives)

revdrw on Thu June 18, 2015 3:20 PM

Year: 1994
Make: Chevrolet
Model: S-10
Engine Size: 4.3
Refrigerant Type: R-134a
Ambient Temp: 90
Country of Origin: United States

OK, I have a '94 S-10 SS 2wd Auto pickup with 134k, nice body, pretty good shape. Have had that truck for 2 years, AC has never worked since I owned the truck.

Just today, I bought some of the refrigerant in a can, and realized that the AC clutch was not working. It will spin manually when engine is not running, but won't turn on. I understand that to fill up the system with R-134, the compressor needs to be running. Furthermore, I know that you can/should "jump" the relay so you can run the compressor and fill system with freon. The problem is that on that truck, I can't figure out where the relay is. There is NO neatly organized relay/fuse box under the hood with all the items labeled. There are four relays on the firewall, but none of them are labeled. I presume one of them is the AC relay, but don't know for sure. SO, can you help me do 2 things.

1How can I find the relay, or determine which one of the firewall relays is the AC, AND
2Exactly how do I jump the relay (please be detailed) so I can fill the unit with freon?

As Elvis would say, "Thank you, uh, thank you very much" for help.

BTW, the AC fuse seems to be good.

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Just a simple man trying to make wise choices.

GM Tech on Thu June 18, 2015 5:14 PM

Much easier to jump the cycling switch connector- it is the one on the accumulator- pull connector off and putg a paper clip in both terminals on the connector-- if you still want the relay- it will be the one with at least a pink and dark green wire-- the cycling switch connector is much easier to do.

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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......

GM Tech on Thu June 18, 2015 5:16 PM

Much easier to jump the cycling switch connector- it is the one on the accumulator- pull connector off and putg a paper clip in both terminals on the connector-- if you still want the relay- it will be the one with at least a pink and dark green wire-- the cycling switch connector is much easier to do.
Oh- and I would not put Freon in it-use 134a refrigerant which was the first year used in 1994-- Freon is the brand name for R-12


-------------------------
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......

GM Tech on Thu June 18, 2015 5:17 PM

Much easier to jump the cycling switch connector- it is the one on the accumulator- pull connector off and putg a paper clip in both terminals on the connector-- if you still want the relay- it will be the one with at least a pink and dark green wire-- the cycling switch connector is much easier to do.
Oh- and I would not put Freon in it-use 134a refrigerant which was the first year used in 1994-- Freon is the brand name for R-12


-------------------------
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......

Jag987 on Thu June 18, 2015 6:33 PM

Wow!! Mr. GM Tech sir, a triple post? What happened there???

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I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

mk378 on Thu June 18, 2015 7:56 PM

If you have zero pressure you should make some effort to find the leak, as it's just going to leak out again rather rapidly.

On the other hand, if there is enough pressure but the compressor won't start, there is a different problem than lack of refrigerant.

Do not use stop leak agents. Fill with plain R-134a only.

Jumping the compressor typically isn't necessary. Compressor will start when there is enough pressure to close the switch, which is about 40 psi.


Edited: Thu June 18, 2015 at 8:10 PM by mk378