We recently converted our 67 Olds from the original freon to R134 and cant get it to cool. Compressor and blower work fine with no leaks in the system. Just replaced the exchange valve with no change and have ordered a POA valve to try that but I'm wondering if anybody has had any experience/trouble with a conversion and if they found some specific tweak or something that the shop doing my work may be missing?

 

Mine had been converted to R134 when I bought the car and it didn't cool very well, that's why I converted it back to R12. Now it's like a refrigerator.

 

Thanks. That thought has been occurring to me so I may just have to do that. But you didnt have the problems we're having with not getting cool or the pressure behind the exchange valve not working?

 

Problem with R-134a conversions, is the factory condensor coil is a bit smallish for this, and cooling capacity at low speeds usually suffers. Assumiming you mean TXV(thermostatic expansion valve) when you mention exchange valve, but you already replaced that anyway. Maybe go back to R-12, if mostly low speed cruising. If not already, good idea giving the system a shot of UV trace dye, for easy leak checking later with a UV light. Another easy thing is giving the condensor coil a good washing. Not to much water pressure to bend the fins though.

 

I changed my original condenser to a cross flow design, made for 134, plus I had my POA calibrated for 134. I get between 22 and 28 degree air through the vents, with very little loss at low speeds or when stopped. Classic Auto Air makes them for various models. I have one for my 72 Cutlass and my 70 Bonneville. Made a HUGE difference! It isn't the compressor, it is the original condenser that can't cool the refrigerant enough to function properly.

 

The latter part makes a world of difference and is the most often overlooked, as the POA valve is so misunderstood by most AC shops. It is old enough that most techs do not know how they operate.
R12 and 134 operate at different pressures, so the POA must be adjusted to match. I think I posted the test procedure here somewhere and is fairly easy to do. Blow compressed air through it and turn an inner adjusting nut a fraction of a turn, while monitoring inlet pressure on a gauge. Sucker will often sound like a half-choked duck, which means it is working...
I need to look for that procedure, as I need to test and cal mine anyway.

 

Condenser up grade when using R134a. Need to condense the hot gas to 100% liquid. Existing condenser can't do it. Reduces capacity. You need to what's called liquid subcooling before the refrigerant goes to the POA or TX valve. Also POA need re-cal or TXV replaced.

Mike

 

Thanks for all the feedback guys! Appreciate the benefit of the experiences and some options for us to try.

 

One of the issue I had in converting over to 134a, was the existing hoses could not hold the 134a gas. The original hoses from my 71 Supreme looked great. The car was garaged all its life in a controlled environment. However when I added 134a, I found over 50 pinhole leaks in the "Compressor to condenser / muffler" hose.
This is a short hose, only approximately 2 feet of rubber and it had a pinhole leak every quarter inch for the whole length of the hose. The "Compressor to condenser" hose seems to be running at the highest pressure and temperature and is expected to be the first to leak.

If you are running original hoses and 134a, I strongly suggest a detailed inspection of the hoses.
I cleaned all hoses with Windex to remove all oil and grime and made the hoses nice and shiny.
Then I fired up the AC and let it run for 10-15 minutes. I inspected all the visible rubber with a bright light and discovered my next big expense.

Looks like ill be replacing "all" 3 of my AC hoses.

7718 Engine compartment overview.
7714 "Compressor to condenser" near muffler end.
7717 "Compressor to condenser" near condenser end.
The little dark spots on the hose are bubbling freon leaks.

PS: Air temp at the center vent is 32F, on a 75F day with stock condenser and 134a.

 

POA valve fixed the problem and we now have cold AC. No leaks in the hoses yet but thanks for the heads up on that so we know what to look out for.

 

I think the 134 molecules are smaller, so "barrier" type hoses are required for reliable service.

Don't chunk the old POA - it can be adjusted for 134 by a simple turn of the adjusting nut inside at one of the main connectors.