A/c question
Thread Starter
Racer
Joined: Jan 2008
Posts: 299
Likes: 4
From: Surprise AZ
A/c question
Has anyone converted R12 to R134. On my 66 I changed over from R12 to R134, kept all the original parts. All of the a/c parts were flushed out before installing them back. When I connect the R134 adapter to the compressor low side, does the schrader valve on the compressor have to be removed? So I can vacuum out the system. It looks like the schrader valve does not push in when the adapter is screwed on. I never done ac before. Any help would be appreciated. 
Melting Slicks
Joined: Aug 2004
Posts: 3,078
Likes: 101
From: Riverhead New York
When pulling Vacuum you will need the Schrader Valve to hold the Vacuum even after the pump is removed. The presence of Vaccuum will insure the ability to add the correct amount of Freon. Check out the ACForum.com for more. Al W.
Pro
Joined: Jul 2008
Posts: 622
Likes: 24
From: Clermont Florida
The new 134 fitting you have to install has its own check valve, so the original schrader valve is not necessary. Some of the 134 fittings will work with the original valve installed, some will not, and some will be damaged by leaving the original schrader in. Been there... broke that.
I recommend removing the R12 schrader. The 134 schrader will do the job by itself.
BTW, did you remove the compressor, and drain the old oil and add 134 compatible oil. The A6 compressor has a sump that holds a considerable amount of oil, besides what flows through the system.
The receiver dryer must be changed also, to one that is compatible with 134.
Initial 134 charge should be 90% of R12 charge, plus 1/4 lb.
I recommend removing the R12 schrader. The 134 schrader will do the job by itself.
BTW, did you remove the compressor, and drain the old oil and add 134 compatible oil. The A6 compressor has a sump that holds a considerable amount of oil, besides what flows through the system.
The receiver dryer must be changed also, to one that is compatible with 134.
Initial 134 charge should be 90% of R12 charge, plus 1/4 lb.
Race Director
Joined: Jun 2006
Posts: 17,901
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From: Inverness FL
St. Jude Donor '07
Bill
Race Director
Joined: Apr 2005
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From: Bowling Green, Kentucky
Be certain that you have the small screen insert on the inlet side of the expansion valve. If not, they are available and can be purchased from NAPA. Part # TEM 207342.
Also, although not required, the revised system will work best if the POA valve is set to maintain a slightly lower evaporator pressure. The POA is adjustable. The AC Forum "67vetteal" mentioned has the procedures for doing this. It may have already been done if you bought a reconditioned POA and specified it was for 134a. You will need every bit of cooling you can get in AZ in the summer.
Larry
Also, although not required, the revised system will work best if the POA valve is set to maintain a slightly lower evaporator pressure. The POA is adjustable. The AC Forum "67vetteal" mentioned has the procedures for doing this. It may have already been done if you bought a reconditioned POA and specified it was for 134a. You will need every bit of cooling you can get in AZ in the summer.
Larry
Melting Slicks
Joined: Aug 2004
Posts: 3,078
Likes: 101
From: Riverhead New York
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Le Mans Master
Joined: Aug 2005
Posts: 6,546
Likes: 1,978
From: Temple Terrace Florida
A/c
If you need the POA adjusted for 134A, or need a new one already adjusted, call Classic Air in Tampa. They are local for me and the shop had about 50 on hand a few weeks ago. Speak to Curtis, he is the manager of the shop and is old school. He set me up with a retro 134a system for my 70 Chevelle. They have been around since 1974. After walking through the shop, it is doubtful they don't have any part you need. Jerry
Burning Brakes
Joined: Jan 2007
Posts: 1,104
Likes: 12
From: Woonsocket Rhode Island
When I bought the retro-fit kit there was a schrader valve in the adapter so I removed the original R-12 schrader and added the adapter. I then proceeded to vacuum the system and test for leaks. It was fine so I added the R-134 and got the system running nice and cool figuring that I would run it a while at low pressure to give the old system a chance to get use to the new and then I would top it off.
I then removed the hoses and what a mess. The new schrader did not hold. I lost the oil and freon but it would have been a great video watching me trying to replace the original schrader while the system was discharging. I actually got it in but the pressure was so low it did not even read on the gauges.
I then started all over again but this time I added only a 1/4 charge and removed the hoses to check for leaks. Second time around everything was OK and the system runs fine with the old schrader in the new adapter.
I then removed the hoses and what a mess. The new schrader did not hold. I lost the oil and freon but it would have been a great video watching me trying to replace the original schrader while the system was discharging. I actually got it in but the pressure was so low it did not even read on the gauges.
I then started all over again but this time I added only a 1/4 charge and removed the hoses to check for leaks. Second time around everything was OK and the system runs fine with the old schrader in the new adapter.
