i recently converted my ac from r12 to 134a. with the kit from autozone. there was no r12 left in my system. so after putting in the pag oil and 3 cans of 134a. the system worked great in the garage for about 1/2 hour at idle. car cooled great. and was pretty proud of myself for spending 40.00 and a cool ac. Now when i get the car on the highway. the fan/ac/clutch does not engage at all. when the car gets to operating temp. although i tried it today on the way home a t 3am and it worked fine all the way home. of course its alot cooler out and the temp on the engine isnt as high since its at nite. is there a relay or switch that maybe needs to be replaced? any help would be appreciated thanks

 

134A operates at a higher head pressure, if your systems has a R12 high pressure switch, this maybe holding out the compressor.

 

did you flush the system before you added the new oil? if not, you will have too much and incompatible oil, which will cause insufficient cooling at higher pressures.