94 A/C Problem

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Northstar Engines and System Technical Discussion Discussion, 94 A/C Problem in Cadillac Engine Discussion; I have been trying to figure out my AC for a little while. I finally got a set of R-134a ...
  1. #1
    51magnum is offline Cadillac Owners Member
    Join Date
    Jul 2003
    Boise, ID

    94 A/C Problem

    I have been trying to figure out my AC for a little while. I finally got a set of R-134a gauges and I hooked them up. The equalized pressure was 150 psi. Is that to high?

    That is not my real problem, the real problem is that the compressor clutch is not engaging. So I know it is not the low pressure cut off switch because I have 12 volts going in and coming out of it. However, I can not find the high pressure switch for the life of me. Is it on the tube going across the fire wall? If it is then which one is it? I would think it is the one before the expansion valve but there is a switch/sensor right after the valve.

    I know the relay is good because I tried it in a different location and it worked. Also, I have a volt meter on the hot side of the relay coil and I do not get 12volts. So from the wiring schematic it shows the power coming from the fuse (which is good, I checked it) and it goes through the low side switch then through the high side switch.

    I have done the diagnostics on the dash and it shows both switches read 0. I am not sure if this means they are OK or they are bad. I know I do not have any codes, so I assume it means they are ok. I am at a loss, I need to get 12volts to the one side of the AC relay so the PCM can ground it out.


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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Woodstock Ill.

    Re: 94 A/C Problem

    If your '94 is the same as my '97 was, the high pressure switch is on the firewall line on the drivers side. Actually, I think that is a high "temp" sensor. The high pressure switch I believe is on (or in) the compressor itself.

  4. #3
    51magnum is offline Cadillac Owners Member
    Join Date
    Jul 2003
    Boise, ID
    Thread Starter

    Re: 94 A/C Problem

    I finally found it. The high pressure switch is on the drivers side right below the radiator. I pulled the plug and checked to make sure I had 12 volts and I did. But when I back probed the connector the switch was not making. So it was a bad switch. Of course a little knock with the ol wrench and presto, it started working. Problem fixed.

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