When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My '81 was converted to R134a over a decade ago. I rarely use A/C, but upon trying to use it for the first time in at least a year, it only blows hot air. I noticed that the compressor clutch wasn't engaging. I took off the connector on the compressor, and I am not getting 12v at the connector. Also, there's a switch further down the fender, across from the exhaust manifold, that I believe is the pressure switch. No voltage there either. I read that I can jump the terminals, which I tried, and still nothing. If it's a refrigerant leak, is there no safe way to engage the clutch just to see if it works? Could I use a bench-top 12v power supply and apply power to the compressor terminals safely? Any other suggestions? Thanks!
By putting the jumper wires across the switch like you did is like trying to turn on a light bulb without power. lol
One of the green wires at the 2 wire rubber boot connector should have 12vdc with A/C on.
If the pressure switch is satisfied it WILL pass voltage through the switch to the compressor clutch through the other green wire.
For testing only, jumper the 2 green wires at the 2 wire rubber connector with A/C ON and the clutch should engage.
one of these. parts store, walmart, amazon, anywhere. 2 cans of r134. there is a pressure (or lack thereof) cutoff which is why no power at compressor plug. first just put the hose on without engine running. no pressure on gauge? start it and feed it 1 can of refrig. now watch the low side pressure and listen to the compressor. fires up and low side starts dropping. under around 25 it shuts off and pressure climbs again. that means you need more refrigerant. you want it to just stay above cutoff pressure at idle. if it doesn't blow cold next week, you have a reasonable leak. if it won't blow cold in an hour you have a substantial leak. if you see it blowing out of the compressor behind the pulley or out of the big black flex hoses, you now know where your really big leak is. most likely scenario is it will hold refrigerant from a week to a month. and since these are not daily drivers you may be ok with charging it twice a summer of so.
Quick question for you, do you still have the factory computer system on the car? The power from the a/c switch runs through the computer before it goes out to the pressure switch you talked about.
nice original car.. for me.
- buy / rent for free 134 gauges
- report pressures
- if you find low and need to add vs completely empty..
- i would add a few ounces of oil as well..couldn't hurt
Unless you see oil has leaked out I would not add any oil. If you wanna be safe a one oz can of precharged oil would be ok. Question is..what oil is in there? If you don't know Ester oil is the safe one to use as it is compatible to any oil or residual oil present in the system.
Adding oil more than the system requires lowers system efficiency and increases duct temperatures.
1981 A/C problems
