RE: [Chevelle-List] a/c conversions

[John Nasta]

You can use a drop in replacement. It is called Auto Frost or R-406A. It works great, and is compatible with mineral oil (as used on R12 systems). Most all of the other R 12 alternatives are really mostly R 134a. R134a has lots of oil return issues and various compatibility issues in addition to its lousy cooling performance. If you want R134a, use it. Don't pay more for a blend of R134a and something else. If you have a CCOT system, try a variable orifice valve.� It improves cooling at idle a lot, and reduces high side pressures and increases compressor life as well. Polyalpha + oil is also a good way to go if converting. It actually lubricates well and avoids the hydroscopic and compatibility issues of POE and PAG. Avoid Freeze 12. It does not reliably return mineral oil. Autofrost, a.k.a. R 406a is a good product and it is a direct drop-in replacement. We sell it for $12/can but you can probably find it locally.   John Nasta Old Car Network http://oldcarnetwork.com     -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of [EMAIL PROTECTED] Sent: Saturday, April 20, 2002 2:49 AM To: [EMAIL PROTECTED] Subject: Re: [Chevelle-List] a/c conversions   Jason, I don't know much about automotive a/c, but I have worked on commercial refrigeration units that were originally R-12 units and used a drop in replacement to recharge such as R-409a and ICOR hot shot without retrofitting ANYTHING.  I just replace the filter dryer with an identical one, and pull a very deep vacum before charging.  I don't know why we can't do this on cars other than the fact that people in the automotive buisness want to make money by selling retrofit kits.  I guess the R-409a head pressure is a little high for hoses, but there are other R-12 drop in replacements now.  The just come in a 24 pound bottle. Can anyone tell me why we can't use a drop in replacement in cars? Pat