I saw a kit in Autozone today for $40 that would switch a car to a R134 AC....does my car have this already or not?? (yeah, I know; dumb question).......and does anybody have anything to say about how difficult it would be to do this??

 

Your '91 should have R-12 from the factory. Unless the charge is completely gone, there is no good reason to switch to R-134A. It is less thermally efficient than R-12 and will stress the system more due to the higher operating pressures. Conversion is not difficult, and yours may be easier if you have an adjustable expansion control device.

 

To be sure what your car has for refigerant there is a sticker under your hood, usually on a black shroud near the firewall or some times it is on your compressor or near the resivoir but on the yellow sticker it will say either R-12 or R-134a