Auto Air Conditioning & Heater Repair: A/C for dummies, r 134, pressure switch

Question
I replaced the a/c pump on my 92 s-10 blazer. I am aware that I need to recharge it with r-12 and will have an expert do that for me since I don't know a thing about a/c.
I only had a couple of questions for my own knowledge.
What is the function of the low pressure switch, and how can you tell which side is the low pressure and the high pressure.
I thought about retrofitting to r-13 but all I hear is negative things about it so I will stick to the r-12.

Thanks,

Juan

Answer
The LOW side fitting is on the accumulator (receiver/drier) and the HIGH side fitting is on the small steel tube.

Retro-fitting to R-134 is not a problem as long as it is done EXACTLY RIGHT. About all you will lose is about 20% of your cooling efficiency of which you will barely notice.


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