Questions and Answers
R-12 to R-134a
Q. I am converting my R-12 system to R-134. The car is old, so I purchased a conversion kit from K-MART. The A/C has not been used in the past few years. I put about 2.5 cans of freon into the system and a can of oil. The problem I have is the compressor will not turn on. I have disconnected the wire in front of the presser switch and jumped it from the battery and the compressor will run. Do you think it could be my switch in the dash?
1989 Geo Metro
3 cyl. 1 liter engine
manual shift
190,000 miles
EFIThank You,
Scott BA. Typically there are three switches that control the on/off operation of the A/C compressor. One is, of course, the dash switch. The other two are the A/C high pressure switch and the A/C low pressure switch. The high/low pressure switches are commonly incorporated into one switch these days. Then you have the A/C relay which powers the A/C compressor directly. Any one of these could cause the compressor not to run.
Without a set of A/C gauges hooked up to the A/C system, diagnosis is almost impossible. You can test the electrical portion of the system to determine if the dash switch and A/C relay are good, but if you do not know how much refrigerant is in the system, you don't know for sure if it is over-charged or under charged. A quick test you can perform on the switch is to unplug it and jump the terminals in the connector. If the compressor kicks on, then you know the problem is in the pressure switch and everything else is okay. If it doesn't, then you need to look at the dash switch, the A/C relay or the wiring.
You should be aware that anyone doing any A/C work must be licensed to do such work and there are EPA regulations that cover the discharge of refrigerant into the atmosphere. There are severe fines and penalties for violations. I would not recommend anyone at home do their own A/C service or repairs.
