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05 grand caravan 3.3L keeps burning up a/c clutch

  1. Van is on #6 Murray a/c compressor (new never reman!) Keeps burning clutch this one lasted 3 miles. Van has correct charge no debris in system always put on 20 minute minimum vacuum time before charging. A/c clutch just seems to fail consistently. Anyone else come accross tjis?

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  2. Have not seen repeated failure....

    I will add some thoughts,
    Air gap,
    Circuit checked - 12v DVOM (not test lamp), AMPs draw, and ground is OK , diode ?
    Nothing else on circuit from relay?
    no voltage on grd circuit
    It does cycle ? What is High ?

    Denso 10S17 – 3.3 amps @ 12V ±
    0.5V @ 21° C (70° F)
    Denso 10S20 – 2.2 amps @ 12V ± WITH REAR AC
    0.5V @ 21° C (70° F)
    Compressor Clutch Air
    0.35 - 0.60 mm (0.014 - 0.024 in.)
  3. Vans scheduled for monday afternoon. Will check electrical and repost. Thnx for input!!!

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  4. I would like to see some colleagues opinions on 'murray' replacement parts as opposed to denso.

    Also there is this tidbit I found
  5. Clarify: is the clutch coil burning up, going open-circuit? Or, is the clutch friction surface disappearing? Or, is the friction surface OK but the mating bare steel parts getting warped? My guess is you have a poor connection in the wiring and voltage to the coil isn't the full 12V (nominal). Check all that as already suggested.
  6. Heading out to trailer van back to shop, thankyou all for suggestions. Will update when i know more

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  7. Ok got it back and we are getting 13.5v @ clutch with engine running. But clutch is burned and not engaging compressor

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  8. Have 7 mv on ground circuit

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  9. By "burned" do you mean electrical failure of the coil? See reply #5, asking for a better description.
  10. Volts isn't Amps. 50PSI water to a Garden Hose is different than 50PSI to a Fire Hose. If this thing is burning CLUTCHES, I'd wire a Relay right at it. Whatever circuit is powering the Clutch now, energizes a Relay that gets its power from the Battery via a Fuse. Did this on a van years ago. Completely different vehicle, a Dodge with an aftermarket A/C using a York two-cylinder compressor. But it kept the clutch engaged and I had no trouble the rest of the time we had the van.
    [​IMG] [​IMG]

    Relay pictured has Normally Closed Terminal 87A, you wouldn't use it for this job.
  11. Friction surface disappears. Lets out a nice cloud, and makes for a pisst off customer.lol[​IMG]

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  12. I'm assuming that if the compressors were locking up internally, you would have mentioned it, so...JD's idea of setting up a relay to assure adequate power to maintain full clutch engagement would be something to consider.
    Another possibility would be a batch of clutches with crappy "rubber springs". But I think I see heat from slippage and if the rubber part broke, the plate would not get hot like that.
  13. I get what jd said but im getting full voltage to clutch so dont quite understand how a relay will help

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  14. Just for fun, how about measuring the current draw of that clutch coil? And, what is the DC resistance of it when cold?

    Can you take the clutch apart and take pictures of the damaged parts "spread out"? I'm not familiar with how that clutch is constructed, not sure what I am seeing in the picture posted.
  15. interesting -
    You said 6 new compressors (post 1)?
    Are the clutches coming on the compressors OR are you installing them?
    What is history - customer brings in with just a bad AC clutch OR more to this.
  16. Yes this is #6 new Murray compressor. Clutch is new with compressor. First (o.e) compressor locked internally. Changed all but evaporator. Now keeps toasting clutches. I have had issues with Murray b4 but this is outrageous. (personally i think Murray is CRAP, but thats another subject) longest living clutch so far was #3 which ran for roughly 3 months and abt.1600 miles (coincidentally winter months where only defrost engaged clutch). Clutch has 3.7ohms resistance cold.

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  17. A couple more pics trying to show rubber debris in clutch[​IMG][​IMG]

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  18. About installing a relay....if a lack of current (which is different than mere voltage)...

    ...if a lack of current occurs at some point (may well be an intermittent condition)...

    ...you can eliminate lack of current as a cause for inadequate clutch clamping power by installing a relay that uses a dependable power and ground connection for the LOAD circuit. The original "wires to the compressor" are used to operate the coil of the relay.

    Yes, I said "dependable power and ground connection", which means you want to be doggone sure your relay LOAD circuit will not also have a problem due to a lack of current.
  19. Another thought...if the "rubber spring" is too stiff, it might reduce clutch clamping force. Set air gap to minimum.

    And if the clutch plates are just too slippery due to metallurgy alloys, well...Murray, you've screwed us again. Call some other stores (Orielly?) to see if they have had problems with that model number.
  20. All those compressors...too much oil in the system would give us different symptoms, I guess?
  21. This is what I call thinking out loud:

    I was thinking As Dan mentioned - too much oil, maybe 'slugging' is that what its called?
    I am sure you run it before releasing it not just idling in the shop but a drive.
    BUT I would suspect the operator would feel something. The changing drag or hear it if belt slipped even a CEL if pressure spiked up - something.

    PS: I did not ask - front AC or front and rear?

    A companion site to BAT specific to AC - might want to give them a shout, maybe someone there will recognize this failure.
  22. In line with slugging oil... What is the High Side Pressure? Pretty sure this new a vehicle would have some kind of High Pressure Cutoff. Just thought that being either charged too high or part of its cooling not working could drive the system into crazy high head pressure and overload the clutch.

    Years back, I replaced a FWD Buick Century compressor. Would NOT COOL. It was a Murray, or Everco, one of those cut rate parts. Was tagged as having the correct oil charge and I didn't check it. Turned out it was full to the gills. Now I always drain, measure, and adjust as needed.

    Anyhow, with all that oil, the compressor did not seem to bog down. Just wouldn't cool.

    Next, I retrofitted to R134A (yes, we had that car a long time. Wife's mother's then wife's then daughter's! Got her through college) Anyhow, that compressor would overheat and cut the thermal switch in the back off. This was a GM DA/HT-6 with switch cavities in the back.

    I traced that problem to the condenser not getting enough air from the OEM puller fan. Added a 16" pusher and the A/C worked well. What I've seen with 134A, is it's fickle on the high side to an overcharge.
  23. Front and rear a/c, pressures have always been normal never had spike on high side. I always drain new compressors and refill dont trust mixing oils

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  24. If the compressor was locking, slugging or high pressure issues - I gotta think there would be a sensation, a code, or a gauge reading.

    Another thought is its slipping itself to destruction due to weak clutch pull in or slipping.... And why does it not show failure in shop.

    What changes down the road.....
    Can you command both fans on and watch clutch under those conditions.... maybe watching for an amp or voltage drop when charging system loaded ....
  25. Ok, took jd's advice and wired in a relay, got all back together. On test found rad/condensor fan #1 had bad connection causing high side to spike to 350 psi. Got fan to kick on and brought high side pressure back down to 200-220ish.

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  26. So, does the too-high pressure switch work? What pressure is it supposed to activate at?
  27. Ok, now we got numbers, now we can get somewhere. Kick off/closing should be @ 400psi.

    Here is a chart for this soccer mom van. Screenshot (89).png
  28. This is telling you something. You can have a bad connection, but still have proper voltage, but no knowing what amps will go through the bad connection, hence most likely not pulling enough amps to properly engage the clutch, hence causing slipping and burnt clutches. Make sense?

    Would have been nice to know amp draw of said 6 clutches before you found the bad connection, but that does not mean the PCM is seeing that and code.

    Can you isolate ground wire of clutch which should be BK wire to ground point G101? Then isolate splice S106 wire BK/GY. Could have a choke point there. The DB/YL is easy enough, you checked that with a new relay setup as advised by JD. But how is your ground path?

    I think Kev2 posted this wiring, but here it is again if you didn't get that.
  29. Most reasons I know of multiple clutches failing is either lock-up, or poor amp draw causing slippage.
  30. Kev2 confirms what I know already. His words. And mine mimic.
  31. I think amp draw was already posted, but here it is again. 3.3amps for the denso model 10S17 @ 21F @12 +- 0.5v. 2.2amps for the 10S20 model @ same v and temp.
  32. If amps are within specs, you must look elsewhere. Especially after 6 new clutches.

    As sherlock holmes likes to say "when you have eliminated the impossible, whatever remains, however improbable, must be the truth?"
  33. Also, don't rule out crankshaft and idler pulley misalignment. Another thing that is notorious on these soccer mom vans.;)

    A misaligned belt could be causing this all along. A misaligned belt will cause such issues as the gap is no longer under specs when under load and misaligned. I hope that makes sense to you, it sure does to me as I have seen that in the past. Just not as often as your experiencing.
  34. Thats funny because they make an aftermarket tensioner because these vans are infamous of throwing belts. But this one has never had that issue. I will check alignment and amp draw in a.m. Thankyou all for your input. I work alone and often other shops only look at me as "the enemy" so bouncing ideas off others can b almost impossible

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  35. Hey, I had my own little shop for 5 or so years. I know what "the enemy" feels like. Especially when you do better work for cheaper.

    Nature of the beast.

    Never leave a stone un-turned. Some is always watching for you to take a false step.

    Keep coming back, you will see that we are not the enemy. Quite the contrary.

    Peace out, have loads of work to do for my new job that pays me to not face the enemy anymore. But it was a freaking blast while it lasted I must say.
  37. Welp, after much frustration and electrical issues beating me to the point of insanity.... Thinkin we got er licked[emoji38]!!! With new relay wired in, new rad/cond. fan pressures are good again. Got 35 psi on low and 240-250 psi high side @ 90f (cant find degree symbol). Ran a/c for abt. 2 hrs with 15 mile road test. Both front and rear system blowing cold. Thankyou all for the suggestions. Will definitely b part of this site if i can figure it out.lol

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  38. R-12 pressures increase at a linear rate, R-134a at an exponential rate, tube and fin condensers could be flushed out, parallel flow condensers are throwaway. Not only good air flow is necessary, but if any debris on the inside, cannot be cleaned, another thowaway.

    Two possibilities, old compressor was seized putting debris in the condenser, or the system was opened without flushing, deep vacuum, and injecting in new PAG oil, a women's facial cream, exposed to any moisture forms a sludge that blocks the condenser. Stick gauges on it, at 80*F high side pressure should be around 225 psi, seen some well over 300 psi, even close to 400, this puts one heck of a load on that clutch, could well be your problem.

    R-12 never had this problem with mineral oil, working on an R-134a system can take many more hours of work. Another sore problem is the evaporator orifice itself, also blocks refrigerant flow.

    Yet another over a hundred year old problem, that radiator is a bug collector restricting air flow, became even worse with aluminum heads, made even worse by adding a condenser in front of it. Even worse with with FWD cars with electrical fans. Can't have air conditioning without airflow. These have got to be kept cleaned.

    Just saying your clutch may not be the culprit, but the victim of these other circumstances. On single drive belt systems that water pump also sees this extra load, namely by the AC compressor putting a huge load on it. Never was a problem before with multiple belts, sure is now, water pump is the weakest link.
  39. Can also be a problem with the clutch coil itself, way to test them is to apply 14 V to them, can use your battery in series with an ammeter. Hook up a charger, if say the current is 4 amps, after an hour or so, don't have to stare at it, that current should go down because the heat increases the resistance of the coil.

    Could run into one where the current increases, even drastically, using a random wound coil with magnet wire, and even though the current increase, the ampere-turns decreases causing a much weaker magnetic field.

    Would not be a problem if layer wound and varnished, but bean counters don't like this.
  40. You are fabulously correct. I have seen many blown clutches due to clogged condensers or just plain as you say, full of shyte or bugs or even just bent cooling fins.
  41. Earlier there was a post indicating the high-pressure switch doesn't trip until 447 psi, and the mechanical relief valve is even higher at 500-600 psi. It seems odd those would be so high if the system can't withstand those reasonably well, including the clutch.
  42. Thats true the cut out is extremely high. But have witnessed it operate at 450psi when cond. Fan wasnt operating properly on a different caravan. But side note: went to parts house today and they offered buying me one from Dodge directly due to Murrays awesome amount of bring backs this month.lol

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  43. They had another guy yesterday get 1 mile out of his

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