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A/C Clutch not engaging

Discussion in 'A/C & Heater systems - HVAC' started by rgoers, April 15, 2006.

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    1. rgoers

      rgoers Member

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      There is a low pressure switch. Without pressure, the compressor will not run.
       
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    3. Vermonter

      Vermonter New Member

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      I just had my AC system recharged and leak tested. I was told it was good to go, but I still have no AC. The compressor isn't kicking in at all, so I plan to do the above steps. One part I have a question on. When you say..."now this time use a 12 volt source without the light and back probe the + POSITIVE wire"...what do you mean by back probe?
      Thanks
       
    4. rgoers

      rgoers Member

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      That simply means to connect a 'jumper' wire to that terminal. On mine, it was the lower pin, as seen when connected properly.

      I don't understand how someone could charge your system, and leak test it, if your A/C isn't working... :(
       
    5. Vermonter

      Vermonter New Member

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      The connector I have has the pins side by side not one above the other.

      Exactly what I thought when I saw the compressor clutch not turning :mad: I could see that happening if the system wasn't leaked tested first, but it was (supposedly). I'll stop in tomorrow to see if he did the test & charge or if his assistant did it. Maybe it just needs to a tad more freon :thumbsup:
       
    6. EvilleDave

      EvilleDave New Member

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      Sorry for the double post in the other thread but this is the thread I was reading when I wrote the reply, just replied in the wrong thread.


      If I'm reading all this correctly I have bigger issues.
      I checked all the fuses and relays.
      I checked the plug at the compressor(no power)
      I jumped the low pressure switch(nothing)
      The cheapo gauge with the kit shows in the red but when I hit the needle valve there doesn't seem to be much pressure in it, I've recharged many times before.

      I can't remember if I checked continuity at the plug but at the compressor side of the plug show no continuity showing either as ground. I'm on a limited income and would like to have this fixed, the wife is on oxygen as it is.


      EDIT: When applying the 12 volts to the compressor do you also have to supply a ground?
       
    7. EvilleDave

      EvilleDave New Member

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      Decided to go out one more time. I tested the continuity on the low pressure switch and it was fine. So I say what the heck, I'm going to try the high pressure switch. There was no room to get into the switch to check for continuity so I just started the car with the AC on and jumped that plug, the clutch started working. I immediately pulled the wire but it stopped each time. I decided to put the gauges on it again and it showed just a bit low when I jumped the plug. I gave it a few "jumps" then hooked the plug back up and it works.

      I'm not sure what the deal was here, maybe just a bad connection at the high pressure plug. Just something else to look at when all else fails. Thanks again to this site, it didn't solve my problem but gave me the kick I needed to look farther into it.
       
    8. james801

      james801 New Member

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      Just found this from you and try n it out. When i hook to the + side then hit the tabs on the AC Comp i cant get a ground off the top or bottom tabs. I know the light is good i tested it by just hitong a bolt on the ac comp and got a good light. How can the plug not be grouned?
       
    9. jimmyjamed

      jimmyjamed New Member

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      The ground will be coming from the harness, not from the compressor side of the connector
       
    10. aryork

      aryork New Member

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      2000 Ford Explorer Limited. I had same problem as the original post. First I went thru the "easy" stuff like fuzes/relay - all good.

      Enough pressure had leaked out such that the pressure sensor would not allow the compressor clutch to engage and thus the compressor would not run. When the compressor doesn't run, you can't charge the system using the usual procedure.

      First I removed the electrical connector to the compressor (small, 2-wire connector). Cleaned off the wires so I could see they were both not black. The white one, I guessed, was the +12V side. I got two alligator clips and clipped them on, and hooked the black to the - side of the battery terminal. Also, had to make sure two things: 1) the metal parts of the clips would not touch each other, and 2) they were out of the way of the belt.

      Cranked the motor, turned A/C on max. Hooked up the coolant recharger to the low-pressure side (on passenger side). Connected the +12V wire to the battery and the clutch engaged and compressor started running. Then went and recharged the system as per the directions. All went fine.

      Turned motor off. Reconnected the compressor clutch connector and was done. Thanks for all the prior posts - that gave me the confidence to do this!

      BTW: this compressor is a 5-cylinder mini-engine all in itself. After seeing how it works, since I had it replaced a couple of years ago, I have a new appreciation of why you need fluid. The fluid doubles as the lubricant. This mini-engine needs lubricant just like your motor - without it you are doomed. So, keep your fluid filled!
       
    11. noxious

      noxious New Member

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      I have the same problem on my 97 5.0 limited. I've jumped both the high side and low side safeties and it still didn't turn on. Then I jumped from the battery with the truck off to the compressor to see if the clutch works. Yep, I can hear and see it engage.

      Hooked to the low side it reads in the normal range for pressure. I guess I should go ahead and jump it while running like the rest of these guys. I'll update.
       
    12. BrooklynBay

      BrooklynBay Moderator & long time member. Staff Member Moderator Elite Explorer

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    13. noxious

      noxious New Member

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      There isn't a relay besides the WOT shutoff I'm aware of. I have the wiring diagram for 97.

      Recharged the system with it jumped at the compressor. Cold air inside. Reconnected factory wiring. No clutch engagement.

      Supplied 12v to the low pressure supply wire, purple, and the compressor kicked on.

      Checked wiring diagram the purple goes to the EATC. Probed purple at the back of EATC and got no voltage with ac on.

      BAD EATC?
       
    14. BrooklynBay

      BrooklynBay Moderator & long time member. Staff Member Moderator Elite Explorer

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    15. noxious

      noxious New Member

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      Well, since I paid 800 bucks for the truck I'm not dumping more money into it. Already had to put shocks on it and remove the air ride BS.

      Since the EATC still operates the blend door and what vents are being using I decided I could make it work. Besides, a mail order repair job is 50 bucks on Ebay and a replacement is 80. I had a few old switches from my nitrous days and wired one up to the purple and acc. Now I just flip the switch which went where the old air ride height selector was. Can't beat free. Even used an old lamp cord for the wires.

      I do have ac gauge plenum so it does have the appropriate charge. The high side and low side switches should still operate so I feel like this crises has been averted. I live in Georgia. You need ac if you live anywhere you might get caught in traffic.
       
    16. JiminIowa

      JiminIowa New Member

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      Mine had the same issue but I had power to one side of the pump connector. According to my schematic, the other wire goes directly to ground, but it has very high resistance so I am going to jumper it to ground and see if the pump will cycle.
       
    17. Zoline

      Zoline New Member

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      Well I may as well comment, my 92 had a bad compressor, eventually the bearings in the pulley went too, swapped the belt and bypassed it. Then by pure luck found a person selling a refurbed compressor for 75 buckaroos, then decided he only wanted 60 for it and delivered it to my front door (woo-hoo!)

      Picked up a new accumulator from the zone (came with new o-rings too holy crap) and a few canisters of r134. During this I'm constantly browsing and researching on this forum and other sites so I can do this perfect. Just happened to have an ac manifold set and vacuum pump AND r12 to r134 conversion connectors laying around from a completely different project that litteraly had absolutely nothing to do with ac systems and was intended for making jewelry... Don't ask...

      So I cleaned and flushed my pipes. Then stuck a new compressor in and hooked it all up and then to the related topic of this thread, I couldn't get my compressor to engage the clutch.

      So I'm thinking maybe my clutch on my new unused compressor is bad. But I didn't give up. Following the wiring I see that the (or what appears to be) low pressure switch is connected nearly directly to my power to the clutch. Testing a bit with my multimeter showed that everything appeared closed including the sensor itself and that I just wasn't receiving voltage. Well I noticed a slimy sorta sticky grease looking material on that very plug when I removed my accumulator. I figure it's some kinda corrosion or something, eventually I'll get around to cleaning it, almost reminds me of old Flux paste sitting on a copper terminal for too long.

      So I figured that that would be the most likely problem area, I've dealt in electronic things, and I know green corrosion just makes for a very bad electrical connection especially at a measly 12 volts. So I have my old compressor funny enough against my gas pedal keeping the Motor at a steady 2k rpm and while trying to remove the plug from the sensor so I could jump it with a paperclip I hear that lovely click from my compressor. Well I was about to give up and drown my sorrows in a few bottles of beer but once I saw that my ac clutch is engaging with the pulley I drop that stupid idea and start feeding more refrigerant into the truck.

      Well I topped it off at about 45 on my low end, not sure why my high is reading a little too high, it might be I'm not understanding how to read or when to read my pressures, doesn't matter, getting what feels like 45-50 degrees roughly and that's at an idle from my vents. So turns out it was, more or less, an infamous loose wire at the pressure gauge.

      Also I will note the pressure should be lower with r134 than r12, or maybe it's higher, I can't Remember. I noticed a flathead screw in one side of the connection points of that pressure sensor. I'd assume the screw is for calibration. Don't know what or why but perhaps some problems could be fixed by adjusting it. Others by cleaning bad electronic connections.

      It was fun hearing the compressor do the clicking from on to off to on again while the pressure wasn't as high, at one point the compressor just clicked on and stayed that way, I think it was about when the pressure read 40 on the low side dial.

      If this was too much to read, then note that it was a bad connection, try jiggling the worst looking point until you get a result, then break out a multimeter if possible. I am dealing with a 92, so it's primarily simple solutions to problems, I'm pretty sure half my vacuum lines are either leaking transmission fluid into wherever, or are just clean broken, yet the only problems I have are with a slight torque converter shudder and a funky driver side rear door latch,and most recently but no longer, an air conditioning problem.

      Yeah, that's all I have to say I guess. Tanks.
       
    18. mweiss

      mweiss Active Member

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      I have a 98 Explorer where this just happened this week. In September, the a/c worked and today, the clutch does not engage.

      Last year, I recharged the system because the compressor was short-cycling and it's blown cold air since then.

      So either ALL of the R134A leaked out in a week, or something else is wrong.

      I pulled the connector off the clutch and hooked a halogen lamp to the connector to see if it was getting power. No power.

      The fuses and relays are numbered, but no indication of what does what function.

      There may be a pressure switch somewhere in the system? (where?) Someone mentioned a diode too.

      It was sudden.. a week ago, it worked fine. Today, nothing, not even a click from the clutch.

      Any ideas where theses switches, diodes and relays are located?
       

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