Been having a problem with A/C clutches burning out on me. It's happened twice with FOUR SEASONS 58096. Cost me $300 each time from RockAuto. Anybody have any experience with some other compressor? Got a better alternative?

Bill

 

Electrically burning up, or the clutch friction material mechanically failing? Big difference.

Jon

 

Clutch friction material mechanically failing. Then heating up the clutch bearing to fail.

 

I wonder if the clutch coil isn't getting enough voltage to stay fully engaged? Thus the clutch doesn't stay fully engaged and begins slipping, thus the friction plate overheating?

I dunno. That might not even be possible with a magnetic clutch. Perhaps it's purely engaged or disengaged.

I'm only two sips into my first cuppa coffee :-)

Cheers
DD

 

It could be voltage drop at the clutch when engaged, caused by a poor ground, poor wiring, bad clutch relay, or high resistance connections. Measuring the voltage at the clutch during operation should give a clue. The voltage shouldn't significantly drop when the clutch is engaged.
Another cause can be severe overcharging of refrigerant, locking up the compressor. Double check how many ounces of refrigerant are supposed to be used. A partial blockage on the high side could also cause the compressor to lock up. A/C gauge pressures should give you a clue if that is the cause.

 

I would hazard a guess that the compressor is getting overloaded, even perhaps liquid in it. Before fitting a new compressor I would have the system evacuated and recharged using a new dryer, and before that maybe a good plan to change the evaporator valve for a new one.

 

One other thing. Is the proper amount and type of compressor oil being used? Some compressors are shipped with oil, others without. Amount of oil should always be verified. Lack of the proper amount orvtype of oil could cause the compressor to start to lock up, burning out the clutch.

 

What is everyone's experience as to how many oz's of R134 refrigerant they've installed from total vacuum down?

 

If you know what the R12 quantity was, here is a chart for conversion of refrigerant weight from R12 to R134a.
https://www.electronicshub.org/r-12-..._in_pounds_lbs

 

Does 24oz of R134A sound right? That's what I put in last time.

 

UPDATE - Got another compressor and its clutch from RockAuto and installed. Put 24oz of R134A in. Still had/have the only 8volts going to the clutch. Troubleshot until I was blue in the face, and I've finally given up. I think the problem is in the Rancor Override switch, but I'm in no mood to take that assembly apart. So... I installed a relay with the 8volts on the pick side and full 12 volts on the clutch side. Problem solved!

 

Okay - now I'm going to ask a stupid question. ALL auto A/C systems I'm used to the A/C clutch cycles in and out to help in the controlling of the cabin temperature. Even though I have the Delanair Service Manual, and I"ve read it dozens of times - especially the intro section where it states that this system regulates temperature by "air blending" - it NEVER occurred to me that the A/C clutch might be ENGAGED ALL THE TIME. I've been approaching all my troubleshooting from the assumption that the clutch picks and releases, again and again.

Can someone in the know verify that this is true for me please?

 

The Ranco thermostat controls the operation of the AC clutch. The Ranco attempts to keep the evap core at (I think) 38 degrees. If the compressor ran 100% of the time it's possible that the moisture that condensed on the evaporator coils would freeze and restrict airflow. 38 degrees is cold enough to cool the cabin but prohibit the formation of ice.

If your compressor is constantly engaged then you're not cooling the evap, the Ranco is bad, or you have a wiring issue.

I will add that unless your system is super efficient, you're unlikely to observe the clutch cycle while idling in your driveway unless the ambient air temp is cool (70 or less).

 

All incoming air is refrigerated first and then warmed (blended) as needed to maintain selected cabin temp. Thus the compressor in "on line", so to speak, in all climate control modes: heating, cooling, defrost, blend.

Any on-off cycling of the compressor is to prevent evaporator ice-up, as mentioned by Thorsen, and is not intended to control cabin temp

Cheers
DD

 

The trigger is 36ºF per the Delanair training manual.

I don't quite agree. Since the trigger is 36ºF the compressor will remained engaged ....and the evap IS being cooled....until 36ºF is reached. IOW, the compressor is still running at 37ºF and the evaporator is still being cooled.

37ºF is plenty cold ! Thus it is quite possible that the compressor won't cycle at all....until or unless the system performance is increased to the point where 36ºF is reached.

For most owners a 37ºF evap core translates to satisfactory cabin cooling except perhaps in the most extreme conditions. Thus the owner may no reason to suspect that his refrigeration system is a couple percent shy of absolute max performance.

Cheers
DD

Cheers
DD

 

Funny, in all these years I never put 2 + 2 together about the clutch staying picked all if not most of the time. Seems like that would put a lot of load/wear on the compressor working like that? And to make things worse, I replaced the viscous cooling fan with two big electric fans years ago. And because the electric fans module/relays have an A/C clutch sensor to keep the fans on whenever the A/C clutch is picked, then the fans are also on all the time. Drove me crazy trying to figure all this out. The fuzzy haze has lifted, and I now understand the system. My flashes of brilliance are humbled by these DUH moments!

 

It dehumidifies the air. That's why you never see a Jag with fogged-up glass


You would think. But the old Harrison A6 compressor is robust. They don't see to fail more often on the Jags than any of the millions of other older cars that used them.

Cheers
DD

 

Agreed, however, I replaced the A6 a long time ago with a Four Seasons 58096. Hopefully it can take it.