The AC has never blown cold since I got it two years ago. The PO had converted it to R134a, I just tried to charge the system and it stopped taking refrigerant at 30psi, should be 45 by chart on can with current temp here. The compressor engages but not cold air and will not take any more. Do I just bring to a shop or is there something maybe I can correct.
Thanks

 

Assuming the conversion was done properly you likely need to adjust the POA valve. It is likely set for R12's optimum pressure of 29.5 PSI? To get maximum efficiency from R134A it has to be adjusted for a lower pressure. Looking into the inlet of the valve (through the fitting where the hose to the Evaporator goes), an adjustment screw with a locknut can be seen. Loosen the locknut and turn the adjustment 1/4 turn counter-clockwise. This adjustment lowered my vent temperatures from 52F to 43F on a 90F day!

 

Also, remember, you do not know what else the PO did or did not do.

Was the receiver/dryer replaced with one compatible with R134?
Was the serpentine condenser replaced with a cross-flow type?
Was the POA valve readjusted (as above)?
Was the system completely evacuated of old R12?
Was nothing but pure R134 installed?

Lots of questions. Often the best thing is to just re-do it properly yourself.

- Eric

 

A few other things on top of what Eric mentioned,

Was the old oil drained completely before it was converted?
Were all of the hoses, o-rings, and shrader valves replaced?

When I was doing conversions in Phoenix we found that the R134 systems usually cooled best when a bit low on refrigerant. We charged them by weight and found that removing an ounce or two often resulted in colder output.

 

I just spent a wonderful 2 weeks going through this. (I'm going on the assumption that you have no hose leaks)


Put your ac on high and place your hand on the POA valve. Is it too cold to touch? If so, you could have a blockage (or a faulty valve) in there. If it is the original POA, you might want to think about replacing it. You can get a new one (already set up for r134) for between $110-$140. While your at it, just replace the expansion valve also. Those can be picked up for $15 at O'Reilly Auto parts.

 

You will also get a better charge in the system if you pull a vacuum on it first. This will insure any moisture in the system is evaporated off. Which will keep the components from corroding from the inside out. A vacuum pump or a shop air driven orfice type vacuum pump is what you need. A Proper set of gauges would be a big help also.

 

Where can you buy a new poa valve calibrated for 134a and for those prices? Are you referring to a poa delete kit which is just a cycling switch?

 

Here are a few links...


https://www.opgi.com/cutlass/1971/co...oning/CH28459/


http://www.classicindustries.com/pro...s/ap2551a.html


Just go to the wonderful world of google and you should find one. I personally got mine from OPGI. Yeah, it is a cycling clutch unit, but it solved my problems. It was a little more expensive, but not by much and I have never had a fitment problem from them.


If you want a true POA, you will definitely spend more (about $190 plus core). Here is another link.


http://www.classicautoair.com/POA-GM-Valves-Home.html

 

Just as I suspected. You were referring to a cycling switch. Would have been nice to know of someone out there selling new real poa valves calibrated for 134a and for that price. Ive got 3-4 of those cycling switches in the shop. Most people prefer a real poa

 

Want to do it right? Classic Auto Air. www.classicautoair.com They can rebuild original POA and recalibrate for 134a. Also, everything that was said previously. Also, buy a parallel condenser. That is the radiator looking thing that mounts in front of the radiator. It cools the refrigerant so it can return to liquid and continue through the system and cool the car. A parallel is much more efficient using 134a. I get lower 30s from my vents, with little loss of cooling when sitting at a light. I live in south Florida.


I bought a Haynes A/C manual and learned a little about the A/C systems and now do it all myself, and have saved a lot of money.

 

Judging by the pictures he posted, it looks like Banny can do this, too.

- Eric

 

Yea that's where ( CAA) I learned about rebuilding poa valves. That was the first thing they taught me

 

Thanks for all the great information guys it is greatly appreciated.

 

Classic is also very good about discussing problems, symptoms etc., to help you fix any problems, and they bent over backward when a compressor I bought failed. It might have been my fault. Neither they nor I was sure, but they replaced it at no charge anyway. Many companies would say it was my fault and it was my problem. Their stance was they wanted happy, satisfied customers, period. I highly recommend them!

 

X 2 on Classic Auto Air...class act.

 

You actually got me wondering (and a little worried) about this so I called classic air this morning. They told me that the cycling switches were being used from the mid 70's on, and that as long as they are hooked up correctly, they have never seen or heard of anyone having a problem with one that was hooked up to an A6 compressor.


Just thought that I would put that out there for information's sake.

 

Two unrelated facts.

Cycling switches were used from the late-'70s onward on the R4 compressors, NOT on the A6 compressors.

Good to know they haven't heard of any problems with them when retrofitted to the A6 compressors, though.

- Eric

 

Seems to me you got someone on the phone that wasn't as knowledgeable for the reputation that CAA has to uphold. Seeing as how they are regarded as the leaders in factory ac systems for classic automobiles. I have my suspicions of who gave you this information but I will wait to see if you remember who it was and can respond. I would call back and ask to speak to Curtis. He's been there a very long time as is pretty knowledgeable. I'm willing to bet he gives you a different answer.

 

I honestly do not remember the guy's name. Sorry.