A/C Clutch Slipping – 2006 Jeep Liberty 3.7

Tiny
FARMERSRIDE
  • MEMBER
  • 2006 JEEP LIBERTY
  • 3.7L
  • V6
  • 4WD
  • AUTOMATIC
  • 132,000 MILES
Here is a real stumper that I’ve been working on for a while, lots of money spent already and no solution.
To recreate the problem the A/C clutch slips under specific circumstances.
1. First make the engine hot enough to engage the viscous fan, do this by running up the rpm in warm/hot weather. Allow the A/C to run while doing this.
2. Bring rpm up to around 3k and cycle the A/C off
3. Wait for the pressures to nearly equalize (about 30 seconds – use manifold gauges if desired) then re-engage the A/C – then we have slippage.
When the clutch slips you can smell burning and you can see the clutch plate turning slowly in fits/starts as if it’s chugging on some liquid or something difficult to compress.
If you re-engage A/C before the pressures have equalized much then it won’t usually slip. If you do it while the engine is cooler it won’t slip, if you do it at low rpm it usually wont slip. I discovered this problem with the OEM setup when we first started towing with the vehicle. The original A/C clutch started slipping when running at high rpm (4k) and high heat, I was rather unaware of the problem at that point in time. I did smell a brief moment of burning clutch smell then the clutch coil went open circuit at almost the same time.
Things I have done since then in chronologic order:
1. Replaced the OEM compressor clutch assembly, this worked for a long while (about a year) then it literally burned up and melted the clutch plate into two pieces while towing through the hot northwestern Colorado desert. The heat destroyed the pulley bearing, melted out the field coil, and I had to perform emergency roadside repair so I bought a whole new compressor (four seasons) because the OEM clutch assembly is not a readily available part. The original A/C compressor turns very smoothly and there is no evidence of internal damage or wear.
2. New compressor clutch also slipped after finishing the first install. Pressures indicated that low side pressure slightly high and high side pressure slightly low (according to the factory service manual).
3. Tested the coil voltage during slipping and across rpm – always at battery voltage. Bypassed engine wiring harness with 14AWG wire anyways just to be sure, voltage stayed the same, clutch still slipping.
4. Measured the clutch gap to ensure it was in spec.
5. Burnished the clutch by engaging the clutch rapidly for 60 cycles (this did not help).
6. Drained the system and replaced the orifice tube, accumulator, and condenser. Oil that came out of the accumulator was clean. Used PAG 46 oil, ran the vacuum for about an hour, waited to check for leaks, measured 560g of R123a using a digital scale, and started the car.
7. High side pressure around 225 low side around 45 at idle (700rpm) ambient air temp around 90-100. Again low side pressure slightly high and high side pressure slightly low.
I have no idea what to do. It blows icy cold air when it’s working but I can’t turn it on because I know it will start slipping during highway driving or towing. Dealerships or A/C mechanics are going to charge me an astronomical amount to fix this and I doubt they will even be successful.
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Thursday, August 25th, 2016 AT 5:55 AM

8 Replies

Tiny
HMAC300
  • EXPERT
First thing is that it takes R-134A not R123A so you have the wrong Freon in it. How many volts is a/c clutch getting? Gap should be.030-, 065" when was belt and tensioner changed last? 60,000 mi is recommended for both. Is the ground at lower right front of engine clean and not corroded for a/c clutch as well as no corrosion on a/c clutch relay and fuse so it gets good voltage? If not clean them off and use dielectric grease on the prongs. Try all of that
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Thursday, August 25th, 2016 AT 12:28 PM
Tiny
FARMERSRIDE
  • MEMBER
MMAC300 - thanks for responding

I did use R-134A, made a mistake writing my original post.

A/C clutch field coil voltage was measured by back probing the connector on the coil it self - this particular coil does not use block/frame as the ground for the coil. Coil voltage was over 12v at all times even while the slipping condition was occurring. A/C clutch relay is clean (no corrosion). Ground on battery has been removed and cleaned. Fuses are intact and clean. I did bypass the engine wiring harness temporarily with larger diameter wire direct to the battery - but the clutch still slips.

Gap is currently 0.020" - this is a brand new Everco 68184 compressor that came preassembled with the clutch.

Belt tensioner and belt were changed 5000 miles ago. Slipping of the A/C clutch plates occurred before and after this repair.

These are certainly the first things to check but I've definitely ruled them out already.

I disassembled the old compressor and the wear on the cylinders looks normal for a compressor of this age. The reed valves all look ok as well as the head gaskets. Compressor does not have any visual signs of damage or ware.

I was considering the concept that maybe one or two (out of the 12 present) of the suction side reed valves might be leaking slightly this could cause reduced system flow which could result in higher than normal low side pressure and only slightly reduced high side pressure (which is sort of what I'm seeing).

I also thought it might be oil slugging so I removed some oil from the system which did not help, to rule out oil starvation I also added some oil which also did not help.
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Friday, August 26th, 2016 AT 3:03 PM
Tiny
HMAC300
  • EXPERT
Well the gap is out of spec which will burn up a clutch but maybe you have a broken desicant bag in accumulator or the orfice screen broken so you may have some gunk in there that isn't supposed to be the system may be flooding.
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Friday, August 26th, 2016 AT 3:15 PM
Tiny
FARMERSRIDE
  • MEMBER
I suspected a problem with the accumulator or orfice tube despite the absence of high head pressures so I replaced both the accumulator and orfice tube (made no difference).

Please consider the statement: Higher than normal suction (low side) pressure and normal to slightly low high side pressure. This is the only consistently abnormal thing I've been able to measure regarding this system and I've replaced everything except for a couple of connecting tubes and the evaporator. Still blows cold air most of the time but it slips when cycled off long enough for the pressures to equalize during high rpm and heavy load.

BTW - the air gap specified in the factory service manual for this car is 0.014" - 0.025" (for the 3.7L)
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Friday, August 26th, 2016 AT 4:10 PM
Tiny
HMAC300
  • EXPERT
Around 45 psi on low side isn't to bad for 90 -100 ambient temp what I gave you was what was in our manual for clutch. Have you tested pressure transducer by compressor? I've got the figures here to check also your high side is low for the ambient you have stated. See chart which leaves me to believe it's something like the orfice. See pics other than that i'll have to leave this open if you recontact me with same problem i'll pass it on.
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Friday, August 26th, 2016 AT 4:37 PM
Tiny
FARMERSRIDE
  • MEMBER
I will check the pressure sensors - haven't done that yet. I will also record some more accurate manifold pressures and get back to you here.
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Friday, August 26th, 2016 AT 5:14 PM
Tiny
HMAC300
  • EXPERT
I'm passing this on
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Saturday, August 27th, 2016 AT 5:37 AM
Tiny
KEN
  • ADMIN
Hello,

I have been working with ac system for over 30 years. On Jeep products they like to run a little low on 134a sometime for what every reason. Try letting a little out and see if you have the problem. It sound like the system is too full.

Please let me know how it goes

Best, Ken
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Wednesday, August 31st, 2016 AT 8:50 PM

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