A/C clutch not engaging?

Posted by eclipsed123, Jul 4, 2012
Newbie Forum - Beginner DSM modification questions and discussions. Common, repetitive, and general discussions will get dumped here from other tech forums. Unless you're a Probationary member you shouldn't post threads here.

  1. eclipsed123

    eclipsed123 Proven Member

    Joined:
    Feb 28, 2009
    Posts:
    72
    Likes Received:
    0
    Newnan, Georgia
    I'm having a problem with my a/c this year. It was working great last year but now it will only blow hot air. The belt is fine, the pulley on the compressor spins, checked the fuses, swapped relays, both radiator fans work, but when I hooked an a/c recharge gauge up the reading were in the red. I think the problem is the clutch doesn't engage the compressor when I turn the a/c on. The rpm's don't drop and you cannot hear anything. Where do you guys think I should start checking next? I am by no means an a/c expert but with a bit of help I can fix my problem.

    Thanks,
     
    #1
  2. slayer450

    slayer450 Proven Member

    DSM Profiles:
    1
    Joined:
    Sep 1, 2011
    Posts:
    326
    Likes Received:
    2
    pontotoc, Mississippi
    There is a high pressure switch and a low pressure switch, if either one is bad the clutch will not engage. Your can unplug one at a time and use a small piece of wire to jump the pins and see which one is faulty.
     
    #2
  3. AlaskanDsm

    AlaskanDsm Proven Member

    DSM Profiles:
    1
    Joined:
    Oct 21, 2007
    Posts:
    849
    Likes Received:
    10
    Phoenix, Arizona
    It could also be that you might have a leak in the system causing you to have less than the necessary pressure to engage the system.
     
    #3
  4. andrew k

    andrew k Proven Member

    DSM Profiles:
    1
    Joined:
    Jun 27, 2012
    Posts:
    41
    Likes Received:
    0
    hallstead, Pennsylvania
    x2 i had this problem before on a 91 mustang gt.
     
    #4
  5. bryanwheat

    bryanwheat DSM Wiseman

    Joined:
    Aug 16, 2004
    Posts:
    6,953
    Likes Received:
    147
    Columbia, Missouri
    The manifold gauge indicated that the pressure was high. I would suspect a bad pressure switch, wiring to the switch, a bad compressor clutch, or wiring to the compressor clutch.
     
    #5
  6. moronthr33

    moronthr33 Proven Member

    DSM Profiles:
    1
    Joined:
    Oct 7, 2010
    Posts:
    169
    Likes Received:
    1
    Aberdeen, Maryland
    Check your coolant level, and what do you mean "in the red" that is most likly your problem. If the system is overcharged or undercharged your a/c will not work.
     
    #6
  7. andrew k

    andrew k Proven Member

    DSM Profiles:
    1
    Joined:
    Jun 27, 2012
    Posts:
    41
    Likes Received:
    0
    hallstead, Pennsylvania
    hmm. yeah was thinking red meant low. but i grabbed an ac gauge that i have 0 to 25 psi = green which is low 25 to 45 (blue) = filled, 45-65 (Yellow) =alert 65psi on up = red warning. this is according to my gauge tho i guess they can be different.
     
    #7
  8. bryanwheat

    bryanwheat DSM Wiseman

    Joined:
    Aug 16, 2004
    Posts:
    6,953
    Likes Received:
    147
    Columbia, Missouri
    The pressure that is in the lines when the compressor is not running would in no way trip a high pressure switch. That would be located in the high pressure side of a system. The pressure in the low side will be higher than operating low side pressure when the compressor isn't running. When the compressor kicks on the low side will drop down and the high side will rise. IF the low side drops below a certain pressure after the compressor kicks on, or doesn't achieve the pressure to begin with than the compressor will kick off. The system would have to be extremely over charged (which would likely rupture a line in the low side) for it to trigger a high pressure switch when the compressor isn't running. The pressure that you see with the compressor off is pretty irrelevant anyway.
     
    #8
  9. andrew k

    andrew k Proven Member

    DSM Profiles:
    1
    Joined:
    Jun 27, 2012
    Posts:
    41
    Likes Received:
    0
    hallstead, Pennsylvania
    is there a way to (hotwire) the compressor to see if it will turn on and get reading from there if it does? or is that a bad idea? this is interesting.. im learning something from this thread as well and more info will help the o.p. in the end :thumb:
     
    #9
  10. bryanwheat

    bryanwheat DSM Wiseman

    Joined:
    Aug 16, 2004
    Posts:
    6,953
    Likes Received:
    147
    Columbia, Missouri
    Yes, you can jump the relay, or just add power directly to the plug. Jumping the relay is the best idea because it will verify that the wiring from the relay to the compressor is good. It would be a real good idea to have your gauges hooked up while doing so to see if the high side is maintaining a constant pressure and that the low isn't being pulled to nearly 0 (a result of low refrigerant). It can damage the compressor if the system is ran with little oil and refrigerant for very long though. This would of coarse just be a short test to check for proper operation of the clutch and to verify that it is a possible problem with the low pressure switch or circuit.
     
    #10
  11. eclipsed123

    eclipsed123 Proven Member

    Joined:
    Feb 28, 2009
    Posts:
    72
    Likes Received:
    0
    Newnan, Georgia
    The gauge I have is for the low side on the a/c line closest to the compressor there are 4 reading on the gauge. Green=Add Refrigerant, Blue=Correct Refrigerant, Yellow=May be overcharged, and Red=May have mechanical problems. Mine reads about half way into the red when connected. I'm not sure where the high pressure switch and a low pressure switch are to test them. I disconnected a plug that is on the a/c evaporator (behind the drivers side headlight) and connected a jump wire between both prongs inside the plug but still got nothing except warm air. When I turn the a/c on the rpms drop a tad, the 2nd radiator fan comes on, and the a/c controls seem to be working fine. Also the air seems to be cooler at the lower fan speeds but when I turn it to full blast it gets warmer. I would like to test the high and low pressure switches if someone can guide me to where they are.
     
    #11
  12. AlaskanDsm

    AlaskanDsm Proven Member

    DSM Profiles:
    1
    Joined:
    Oct 21, 2007
    Posts:
    849
    Likes Received:
    10
    Phoenix, Arizona
    http://www.dsmtuners.com/forums/151989574-post2.html

    Here is the links to the service manuals, they may be of some assistance here.
     
    #12

Share This Page