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1989 Cadllac Brougham
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202 Posts
Discussion Starter #1 (Edited)
Hello,

Today i went to a AC refill workshop and asked about refilling my AC and if it was still possible to fill the old gas, (which it wasn't)
Anyhow, my system which i though was empty was not, it was filled with 50psi air according to the AC guy (no idea why), So i am delighted to know that my AC is not leaking.
He went on and filled R134a compressor oil and afterwards started filling my system with R134a gas...but my compressor would not engage, The AC guy called his boss or similar and asked for advice filling a 89 Cadillac with gas and eventually he told me that my compressor would not engage on R134a because the system did not recognize the gas. However if i changed ac filter and oil it would work, he told me??

I feel confused, have any of you guys "converted" your AC or have you got it to work by DIY R12 substitutes like RedTek or Enviro Safe? :confused:(R600a/R290 propane)
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,737 Posts
You by pass the low pressure sensor on the dryer to engage the compressor (jumper across the 2 wires on the plug). Or erase the low A/C pressure code in the body computer. Filter? He must mean the receiver dryer. My Sedan Deville was filled with Propane for years. The green bottles you barbecue with! The air you had in it was probably added to find a leak prior to your purchase? On that age of car, replacing the dryer is not a bad idea but this in itself wont engage a compressor. You are either mis stating what was said or these people are idiots! A/C systems recognize pressure, not brand or type of refrigerant.
 

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1989 Cadllac Brougham
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202 Posts
Discussion Starter #3
I tell you, he told me that it would not engage because it was wrong gas :suspect: Maybe they are idiots:yup: If i by pass the low pressure sensor, will it engage/disengage as usual? (as in not running all the time)
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,737 Posts
You by pass the pressure sensor long enough to add Freon. THEN... you plug the wires back onto the sensor. Your question was how can I get the clutch to engage to add Freon. I say again, A/C systems only measure pressure, not the type of refrigerant used. I'd find another shop!
 

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1992 Fleetwood S&S Hearse, 1993 Buick Roadmaster
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567 Posts
I've done the conversion myself, and what they say above is 100% correct. Once you jump the two wires, you could fill it with helium of nitrogen, and it would eventually kick on. I might not work well or it might explode, but it would eventually kick on. The guy you took your car to is bad. Very bad. Find a new guy. Quick!
 

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1985 Fleetwood 75
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345 Posts
I am assuming that the HVAC person was able to remove all the old mineral oil from the system and he would also have to change the accumulator with a new one with desiccant that is compatible with the PAG oil that
would have been put in to be compatible with the R134. On the accumulator there is the low pressure cutout switch. this can be unplugged and short the plug to fool the BCM to activate compressor to allow you to charge
the R134 gas. This system uses temperature probes on the high side before the orifice valve and a temp sensor just on the low side after the orifice valve. the BCM will monitor the rate at which the temperature drops
on the low side and thus the pressure on the low side. It should turn off compressor at -2C and back on about 10C. The gas has temp/ pressure characteristics that are different than R12. The BCM is able to confirm
different pressure drop curves and probably go into a fail
mode and kick into ECON. R134 has higher pressures than R12 and also changes temp at a different rate than R12
I have used Redteck in my system and it works good as it looks very similar to R12 characteristics for temp drop on low side. also it will work with old mineral oil.
I hope the teck got out all the mineral oil with a flush. Also if the compressor is a DA type it may not handle the pressure of R134. Replace compressor with a HR6 type.
The BCM will turn on the radiator fans when the high side temp reaches a certain temperature, again this affects the low side temp slope. this slope is part of the BCM programming and at present not
able to change as no code available.
It is possible you may need to change the condenser with a newer cross flow type that has more efficiency than the original that was in the car. R134 has higher pressures and not as efficient.
Make sure the low and high side valve ports were upgraded to the new snap on connectors for R134 to inform techs that R12 was removed. and comply with Gov regs.
I also installed a filter/drier onto the liquid line just coming out from the condenser to help clean and protect the orifice and compressor.
 

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1989 Cadllac Brougham
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202 Posts
Discussion Starter #10
I know, but i am overseas in Sweden and most of the sellers won't ship outside USA, i am also worried about what the Swedish customs will say if they open the package. But yes, i am considering getting hold of R12.
 

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1989 Cadllac Brougham
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202 Posts
Discussion Starter #12
I am thinking of getting EnviroSafe refrigerant (propane made specialized for AC) and fill up my 89 Brougham. I know that propane gas is denser than R12 and R134a so you will need less. What i can't find anywhere (not even in my workshop service manual) is how many PSI the low pressure side shall have when fully loaded since it just says how many oz of R12 to add in a empty system (by placing the gas cylinder on a scale) i am guessing around 50-60 PSI?
 

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1980 FBC
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980 Posts
Propane might be safe for the environment but it will make a spark into a large explosion in an accident situation.

Nevertheless garages in New Yawk City used to use it a lot in AC.

I have not heard of any chunks of Earth missing from a Propane HVAC explosion, yet.

Old refrigerators used sulfur based gas 80 years ago!

Your system has a magic low side pressure happy number. IIRC it is around 37.5 PSI with an average heat load. I can almost see it on the 1978 Snap-On air conditioning machine we used to use.
 

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1983 FWB (Mac), 1981 SDV (Junkyard Dog)
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734 Posts
I don't see a button here for me to push to express "like" to this reply. But then I have yet to use the button. But APEMAN'S answer I like.

Cheers........R.
 
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