AC question
Team Owner
Joined: Oct 2000
Posts: 96,443
Likes: 9
From: Fort Knox, KY
Cruise-In IV Veteran
Cruise-In VI Veteran
Cruise-In VII Veteran
Cruise-In VIII Veteran
So does that mean you can't (or shouldn't) combine R12 with Freeze 12 without first evacuating then thoroughly flushing the system? 
I'm no HVAC pro like yourself, but I thought that Freeze 12 works with existing mineral oil in an R12 system and does not require lubricant replacement like R-134a does.
I'm no HVAC pro like yourself, but I thought that Freeze 12 works with existing mineral oil in an R12 system and does not require lubricant replacement like R-134a does.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Yep - as posted - mixing refrigerants can effectively double operating pressures. Right now - if it's got something in it (R12 or R134), the high side is reaching, on average, 230 psi or so on a 70 degree day before the coolant fan kicks in and that can go up 10 to 20 psi for each 10 degree rise in outside air temp even with the fan running. The High Pressure Limit opens at 400. The pressure relief valve sprays at 600. There are horror stories of Walmart Parking Lot blowups as individuals dump in whatever they've just bought into broken systems. It's not an everyday occurrence because everything that was in these cars has often leaked out. Freeze 12's claim to fame (if I remember right) is that it's compatible with the leftover, residual mineral oil, used with R12. There is nothing complicated about mobile (or home for that matter) a/c systems - I've had few mobile systems that made it through the warranty, but if you start fresh and leak free they seem to work better than what you started with.
Burning Brakes
Joined: Dec 2005
Posts: 819
Likes: 3
From: Flowery Branch Ga
Freeze 12 is ok to mix. But you still have to change the fittings on the car or get an adapter. I mixed freeze 12 4 years ago with the R12 that was left over in the system and it still cools good. They sell a conversion kit on their website. I got mine off of Ebay.
Melting Slicks
Joined: Jan 2009
Posts: 3,482
Likes: 196
From: folsom california
actually 134A is the more efficient refrigerant and it cools better than r12, but only at higher pressures; retrofit it to an r12 system with a lower pressure compreesor and its not as efficient. This is the reason most 134A retrofit change overs that utilize the r12 compressor fail to give satisfactory performance.
