I actually used to do the opposite to improve fuel economy....haven't done it in a long time, but I used to unplug the harness going into the compressor from October - May. That compressor couldn't kick on with the defrosters. It'd help gas mileage...a little. I'd wrap electrical tape around the plug and the harness to keep moisture out.

Going back to original post regarding conversion to R134a, I'm interested in the method you selected to make the conversion.

Nope. The A/C compressor kicks on everytime you turn on the defrosters. Furthermore, there'* no truth to your thoughts in R12 systems... They, too, kick the compressor on whenever the defroster is turned on.

I brought mine in to get done. The test your system to make sure there are no leaks, pull out the R12 the right way, put the fittings on to convert it over, then go through the process of adding 134-a. Pulling vacuum on the system for 20 mins or something like that, then adding the r-134-a and adding the oil needed.

If I am not mistaken, you need less R-134-a than the R-12 so you can't go by how much pound wise it says to use of the r-12.

Usually u can use the same amout of R-134a as R-12. Personally i prefer R-12 because it'll cool faster and colder that the R-134a MOST of the time. That doesn't mean i havn't felt some COOOOLD R-134a systems. We stopped refilling R-12 systems last spring at my shop though, one because R-12 is, well, illegal. And 2, we could get a 50 lb. can of it but do u have any idea the cost to grab some of that stuff? 1200 dollars! A 50 lb. can of R-134a costs about 60 bucks. As far as the A/C running, i agree with the statement that it will only run at a certian ambient temperature. Below that you're running the risk of blowing seals because of it being so cold. We all know what kind of cool our systems can pump. My car'* A/C bit the dust long ago so i don't have to worry about it.