A/C gauge setup question.

I'm in the process of getting my A/C converted over to R134A. I need to know where to hook up my gauge setup at. Do I have to have 3 gauges? The book I have on general A/C shows a 3 gauge setup. The back line has a port the compressor has a port and the front hose has a port. This will be my first attempt on this kind of setup.
I just need some clarification. Sorry if this sounds all jumbled up.
Thanks.


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I dont know what you mean by 3 guage setup. I have never seen that. There is low side and high side. Post a picture of what you are talking about if you can

You are speaking about the compressor inlet service port. According to the service manual, the 3 pressure gauge setup was primarily used only on R-12 Systems with an epr valve. Since you are converting to R-134a, you should remove the epr valve from your setup. Then you will use the two gauge setup, high pressure (discharge side of the compressor) and low pressure (suction side of the compressor). You will need to install 134 adaptors on the R-12 valves .

Ok thanks. Makes more sense now.


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Are you using the stock AC system ? The 3 gauge setup was to read the low side at the comp after the EPR valve as they only used that hookup to test the EPR valve. The other 2 are hooked to the high side and low side before the EPR valve. If you are using the stock system you cant remove the EPR valve or the evaporator will freeze up after its on for a bit. The EPR stands for Evaporator Pressure regulator valve and it keeps the low side pressure from dropping to low and causing the evaporator to freeze up. You have to have some type of control to keep the evap from freezing up. Most newer cars use a cycle type setup on the comp control circuit and some use variable displacement compressors. Older GM and Fords used a Suction Throttle valve which did the same thing the Mopar EPR valve does. You dont have to use the third gauge fiting on the comp cyl head to charge the system. Course you have to add the 134 connectors to the high and low fittings as was said and then charge it through the low side fitting thats on the back of the comp. That should still have a sight glass on the receiver drier that you can still use to get the charge close to right. Ron