Air Conditioning Conversion Question...

Deep6

Registered User
It's hot. I've actually got two questions.

First my 95 has been sitting a while. I noticed that when I go to use the air conditioning- it doesn't engage. I can turn the compressor clutch and when I hooked up a gauge to the low side service port, it looked like it was a low charge like 20-25psi.

Think I should hit it up with a fresh 8oz charge of 134a and see if the A/C starts working again? Any special precautions? What should I look for?

Second on my other "SC" (Saturn) I converted it from R12 to R134a. I did that at the end of last summer and I added about 18oz of 134a and 4oz of Ester/stop leak stuff. It seemed to work fine for a week but then I stopped using the A/C (cause the weather cooled off).

Today in the scorching heat, I went to use the A/C and it kicks the compressor in but there is no cooling. Hmmm. I hooked the guage up to the low side port and it indicated that the system was way overcharged, something like 75psi.:eek:

decided to vent some out and brought it back down to about 40psi but the A/C never got cold at all. Compressor was still turning, so I thought I should let off more and brought it down to 25 psi and now the compressor stopped turning (probably too little pressure). I'm stumped? Maybe I added too much oil? Any ideas?
 
First my 95 has been sitting a while. I noticed that when I go to use the air conditioning- it doesn't engage. I can turn the compressor clutch and when I hooked up a gauge to the low side service port, it looked like it was a low charge like 20-25psi.

Think I should hit it up with a fresh 8oz charge of 134a and see if the A/C starts working again? Any special precautions? What should I look for?
If the engine wasn't running, then the 20-25 psi is too low. Static pressure on a hot day should be 40-70 psi.
You could try to add refrigerant, but the fact that it lost some means there's a leak that needs to be fixed. If there's nothing in the lines, I'd swap out all the orings. Look for oil/dirt around the spring lock fittings and the charging ports.

It would be a good idea to install a new accumulator... BTW, I have a new one for a 95 that I got off ebay but it didn't fit any of my 90 tbirds. :rolleyes: So if anyone's interested, shoot me a PM.

Second on my other "SC" (Saturn) I converted it from R12 to R134a. I did that at the end of last summer and I added about 18oz of 134a and 4oz of Ester/stop leak stuff. It seemed to work fine for a week but then I stopped using the A/C (cause the weather cooled off).

Today in the scorching heat, I went to use the A/C and it kicks the compressor in but there is no cooling. Hmmm. I hooked the guage up to the low side port and it indicated that the system was way overcharged, something like 75psi.:eek:

decided to vent some out and brought it back down to about 40psi but the A/C never got cold at all. Compressor was still turning, so I thought I should let off more and brought it down to 25 psi and now the compressor stopped turning (probably too little pressure). I'm stumped? Maybe I added too much oil? Any ideas?
You need to check the hi side pressure. Could be the compressor is broken. 70 psi might be OK if it was sitting w/o the compressor engaged. When it kicks in though, you should see the hi-side go up and the low side go down. Usually the compressor will shut off for a short time when the low side reaches 25-30 psi and then turn on again.

At least thats how our A/C operates.
 
yes the low pressure switch prevents the clutch on the compressor from engaging when the pressure drops below what its set at usually between 20-25psi

a bottle of freon would be a good idea, make sure it has oil in it and fill it up using a gauge, don't overfill it and get freon that has uv dye in it.

that night after you charge it let the car sit and cool off then get a uv light and search for anything that glows.

oh yeah btw, all freon is the same, no brand is better than any other so don't let anyone fool you, just as long as it has oil in it its fine.
 
Might want to try "r134A" as you need an EPA license to purchase freon. :rolleyes: Its also considerably cheaper.
 
they have a new product that come out last summer called frezze 12-not for use in R134a systems,but for the old stile freon you can buy this otc.
 
Its common for Saturn compressors to stop pumping. Everyone I ever replaced on a Saturn ran but wouldnt compress.I am an ASE certified A/C tech and will tell you that Freeze 12 is a combination refrigerant meaning its a combo of existing refrigerants which almost always is very hard on compressors due to higher vapor pressure.If all components are up to snuff a R134a conversion works as good as R12.
 
Maybe I'll start over again....

I'll see about getting to the T-bird with a quick shot of 8oz of r-134a. But that will be on the back burner for now since I'm not driving it anymore.

The saturn on the other hand is my beater and I really could use the cool air in this unbearable heat.

I got the "interdynamics" conversion kit last october. Since the system lost all of it's R-12 charge due to a faulty schrader valve on the low side port. Once I figured out that was the problem (I could hear it hissing when closed), I simply purchased a new A/C schrader valve and the tool to replace it with. No more hissing.

I then converted to the r-134a by starting the engine, turing on the a/c switch and pumping the refridgerent can onto the low side port. After a few minutes- the compressor kicked on and I was getting cold air. I then emptied that bottle (it was a 12 oz bottle) and then I added about 4oz of r-134a stop leak oil to the system. I checked the pressure again and it was a little low about 30psi and I added about 6 more oz of 134a. Put the cap back on and let the system run for about 15minutes. It was pumping out very chilly air. I used the A/C a couple of more times that week and it worked quietly and without fail. I figured I was good to go.

But now in june- as described above the pressure on the low side was 75psi (indicating an overcharge) and the compressor was in fact kicking in but no cold air. I bled it off but still no cold air. I bled it off some more and now I guess there is too little in the system for the compressor to kick on with.

It is old, does this sound like a compressor failure? Maybe I should just empty it out again and start over? Did I add too much oil with that stop leak stuff? Could that be causing the problem?
 
I am an ASE certified A/C tech and will tell you that Freeze 12 is a combination refrigerant meaning its a combo of existing refrigerants
Also, Freeze-12 has nothing to do with R-12/Freon(tm). Just a label made to improve sales by making people think its a freon substitute. It performs no better than r134a and maybe not as well. :rolleyes:
 
It is old, does this sound like a compressor failure? Maybe I should just empty it out again and start over? Did I add too much oil with that stop leak stuff? Could that be causing the problem?

Maybe. You need a high side pressure reading to know for sure.

I would say no. Your results will probably be the same.

Doubt it. If it was working, then oil isn't the problem.

Possibly. I would never use stop leak in any of my cars. It does rotten things to the insides of the lines, Otubes, expansion valves, and makes it difficult to repair things.
 
Saturn compressors are a known weak link to those of us in the business. They dont like to be converted to R134a unless they are in new condition,these systems need to be flushed of all R12 oil and have 8oz R134a compatable oil added with a new dryer.Particular attention needs to be paid to avoid overcharging the higher pressure of a slight overcharge is fatal to these weak compressors.All these compressors I have replaced have just quit pumping. If your low pressure reading =high pressure that is what you have. Do your self a favor and replace the expansion valve too the new one wil be calibrated for R134a.
 
I think you're right GarSC....

I think you're right man. I can't understand why I've got pressure in the system and there is no cold air whatsoever. I went to run the system today and it ran just fine and I checked the pressure it was 45psi- high but not in the overcharge area. But no cold air just like last time.

It's interesting that I bled refriderant off 3 days ago and I come back to it today and it went up to 45psi.

I added a little more refridgerant and it's up to about 60psi and still no cold air. Maybe the expansion valve is not opening?

I can't get a reading off the high side port since the guage and adapter supplied with the a/c kit will only read the low side. I suppose I could swap the low and high side connectors. Is that safe to do once? I know the instructions warn against that.

I don't know, maybe I should just take it to firestone or midas when they are offering their "A/C Special" and they can just tell me if the compressor is toast for sure.
 
I can't get a reading off the high side port since the guage and adapter supplied with the a/c kit will only read the low side. I suppose I could swap the low and high side connectors. Is that safe to do once?
If the compressor is busted, nothing would happen. If the compressor were working properly, it would probably peg the needle all the way over and might goof up the guage.
I don't know, maybe I should just take it to firestone or midas when they are offering their "A/C Special" and they can just tell me if the compressor is toast for sure.
Probably a good idea at this point.
 
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To do A/C with any accuracy you need to have a SET of gagues which connects to and high side at the same time. Otherwise there is no way you can tell whats happening. When the Doctor takes your blood pressure he looks at 2 readings the systolic and dystolic /high pressure and low pressure.These pressure readings are used with other procedures to diagnose problems.Adding refrigerant NEVER fixes a problem.If it needs refrigerant it has a LEAK. Eventually what happens is you charge the system many times it also leaks out oil which isnt added in the appropriate amounts and the compressor is damaged.These are called A/C SYSTEMS which means everything is designed to work in unison. When repaired EVERYTHING has to be up to spec, otherwise it wont work very long. NEVER charge a system without a complete set of gagues overcharge is your worst enemy. Good Luck
 
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