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.
have the same problem?
Thursday, August 25th, 2016 AT 5:55 AM