r12 to r134
Team Owner
Joined: May 2001
Posts: 29,745
Likes: 3
From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
CI 6-7-8 Veteran
CI-VIII Burnout Champ
St. Jude Donor '06-'10, '13
to do it right you need to drain the oil from the compressor, flush all the lines, the condenser and evaporator. Replace the dryer and orifice tube. Use a vacuum and pull it down to negative 29 psi and make sure it holds for 1/2 hour. Then make sure to add the correct oil and add 134a using a gage set. Replace all the o-rings too.
Autozone rents the vacuum pump and gages for free, just give them a credit card and they will pull a $300 deposit, which you get back when you return the parts.
My system originally held 3.75 lbs of R12, I put in just about 80% of that in 134a. Main thing is to keep the low side pressure below 45 lbs, and better yet, at or lower than 40. (36-40 seems to be the spot). Any more than 40-45 psi and it will just cause problems.
I got mine to blow 59 degrees on a 95 degree day. A neighbor redid his 1981 and got the exact same results - around 40 psi and 59 degrees.
