The title pretty much sums it up. After searching, I've read that the R12 and R134a systems are nearly identical, so perhaps the pressure switches are the same as well. I know a guy who has done some retrofits and he says that I should at least change the low pressure switch (assuming it will be different).

 

I don't think you need to do this. The low pressure switch just turns off the compressor when it gets too low right? So, its looking for a VERY low condition, which should apply to either refrigerant I would think. I'm sure mine didn't get replaced when it was converted. I have since "re-converted" and gone with Autofrost, but nowhere in my fairly extensive research did I find anyone suggesting that you do this.

jds

 

I agree about the low side pressure switch, it's looking for nearly empty system, doesn't matter a lot between r-12 and r-134a. The high side over pressure switch does matter some as 134a runs at higher pressures. However IMHO, I left in the stock r-12 pressure high side as 134a runs under higher condensing pressures and I hate to subject the compressor to pressures in excess of 350-375 PSI. In really hot weather it will occasionaly cycle the compressor on and off to keep the highside below 350 or so. The one thing you can do is make sure you are getting all the airflow through the condensor you can possibly can. I was considering making my Fans run on high speed when the A/C is on to help lower the high side pressures.
Jay

 

Double post, Apologies

 

Which switch is located under the dash, passenger side near the blower? Mine has gone bad and the system will only kick on when you bypass this switch. The sensor has a probe that feeds into the box under the dash.

???

 

JONSKI,
I wouldn't worry about any pressure switches. I've done several conversions on a variety of cars and have had no problems of any sort reported.
The system should take care of itself, pretty much.

 

yup, I've done it several tiems as well, no need to mess with those things. Although the a/c isn't so cold anymore after doing the retrofit. You might watn to try to find r-12 or a r-12 substitute.