Automotive Air Conditioning Information Forum (Archives)

RandyJ on Wed July 04, 2012 1:59 PM

Year: 1989
Make: GMC
Model: C1500 Pickup
Engine Size: 5.7 L
Refrigerant Type: 134a
Ambient Temp: 95
Pressure Low: 100
Pressure High: 100
Country of Origin: United States

Okay, here is the story:

The original system had R12 and bled down to 0 PSI 8 years ago and I never fooled with it. The factory lable says it hold 2.5 lbs of refrigerant. Last week I bought a conversion kit to convert the system over to 134a. I installed the kit and needed to first find the leak. I pulled a vacuum and after about 30 minutes I had lost about 1/6th of the vacuum. I pulled a vacuum again and (started engine turned on AC etc...) and attempted to charge the low side with a can of 134a with UV dye. Well , unknown to me the small gasket inside the fitting for the can was damaged so as soon as I punctured the can it started leaking refrigerant and dye. I quickly pulled the AC cycle switch connector off the side of the accumulator/dryer and jumped it with a paper clip to get teh compressor to turn on to help pull as much of the 134a refrigerant/dye into the system before it all leaked out. I'm guessing I probably got 4 -5 ounces into the system (out of a 12 oz can). I then changed hoses to a good one and added another full 12 oz can. I continued to cycle the compressor sporatically off and on with my jumper while I added the 12 oz can. At this point both the lowside and high side pressure gages read 100 PSI. I decided it was unsafe to continue so I turned off the engine and shut everything down.

The good news is at this point I could hear a hissing sound. Leak found. The hissing was coming from the AC cycle switch. Apparently it was blowing right through the middle of the switch and coming out of the electrical connector.

Now that the leak is found, my plan is to replace the accumulator/dryer and the AC cycle switch. I'm pretty sure that I have other issues though. I hoping you experts out there will be able to give me your opinion as to what step I should take. Any ideas?

Thanks,
Randy

GM Tech on Thu July 05, 2012 7:49 AM

you got lucky.. replace the cycling switch.

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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......

RandyJ on Thu July 05, 2012 8:30 PM

So does that men everything else is normal? I should only replace the cycling switch and dryer. What about the low side pressure being 100 PSI. The same as the high side?

GM Tech on Thu July 05, 2012 10:31 PM

100 psi is normal on both sides with compressor cycled off...

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