My 2 cents from watching a friend convert his Firebird: If the system is charged with R134a the compressor will continue to compress the refrigerant as it had done before, the HX'ers, namely the condensor and evaporator will exchange heat but will not be optimized for this refrigerant upgrade so performance will fall off slightly. This may not mean much to you in mild climates but here in the central valley of California it is quite noticeable. There is also an issue with lubrication and sealing. You must add in the a new lubrication, called PAG oil. The o-rings in the system were NBR materials, it was recommend that they be converted to HNBR o-ring seals. It has been shown that either the R134a or PAG oil attack the NBR o-ring seals. If you do convert remember to have the system evacuated of air prior to adding the R134a and PAG oil. Also remember to keep an eye on the charge level. A low charge level will lead to a loss in performance but more importantly will lead to a sharp reduction in lubrication circulation, which will cause wear to the compressor. R134a refrigerant is an HFC type that has been "shown to cause zero depletion to the ozone layer", I am yet to see convincing evidence that R12 depletes the ozone. In fact in my 10+ years as a chemist I have seen studies that show a greater a correlation to ozone depletion by the methane that is given off from cows belching (I kid you not). -SweatyEddy ------------------------------------------------------------------------ eGroups.com home: http://www.egroups.com/group/dmcnews http://www.egroups.com - Simplifying group communications