Unique AC compressor issue

[eaglescout526]

I might be the only one with this issue but my compressor after coming down from high RPMs after a 20 min drive slips and doesn’t stay engaged unless the RPMs climb or I get out and smack the clutch with a wrench to engage. I have a feeling the magnet is hating the high heat it is enduring out here. It runs absolutely fine in the morning which points me to heat soak issue. But I’m curious if anyone else has this or if it’s just me on the surface of the sun.

[gogmorgo]

Possible heat-related voltage loss? But it does sound like a clutch problem, like it’s on its way out. Can’t say I’ve seen it on an a/c compressor but I have seen similar issues on other electric clutches. In particular a road salt spreader. Half the time it was a wiring issue, not allowing full voltage to it, but sometimes it seemed like maybe it was just full of grit, or internally shorting. 

[cruiser54]

Aren't there shims that can be removed to tighten the clearance between the outer and inner clutch surfaces? 

 

Heck, I'd try spraying brake cleaner between the two and see if a bunch of old clutch material washes out first. 

[eaglescout526]

15 minutes ago, gogmorgo said:

Possible heat-related voltage loss?

This actually wouldn’t surprise me. I’ve had a couple relays for the compressor “die” from heat soaking and a new cold relay would solve the issue. The compressor is NOS but that doesn’t mean it doesn’t have issues, I think it’s 30 years old but still had mineral oil in it so it was for R12 before the requirement. 

 

Just now, cruiser54 said:

Aren't there shims that can be removed to tighten the clearance between the outer and inner clutch surfaces? 

 

Heck, I'd try spraying brake cleaner between the two and see if a bunch of old clutch material washes out first. 

I don't know about any shims, I’ll look but the brake cleaner is a good idea to try. 

[cruiser54]

 

[Minuit]

May also be worth checking pressures to make sure system pressure is not excessively high relative to temperature.

[eaglescout526]

1 minute ago, Minuit said:

May also be worth checking pressures to make sure system pressure is not excessively high relative to temperature.

Would this cause my clutch to act funny? I thought about the pressure from the system but couldn’t find a link between the two as it runs fine for the first 15 min. It’s after that fact when the clutch slips and is “engaged” but acts like it’s not engaged. 

[AZJeff]

Checking pressures when hot are ALWAYS a good idea when diagnosing compressor issues.

 

That said, my thought is that your clutch is suffering a slow heat related failure.

[Minuit]

18 hours ago, eaglescout526 said:

Would this cause my clutch to act funny? I thought about the pressure from the system but couldn’t find a link between the two as it runs fine for the first 15 min. It’s after that fact when the clutch slips and is “engaged” but acts like it’s not engaged. 

What I'm saying is, you may have an excessive high side pressure causing your compressor to experience too much resistance. It's more likely to be something with the clutch, but checking pressures is such an easy first step that it should never be ignored.

[eaglescout526]

Just a quick follow up, I tried cruisers method to just spray the clutch with a cleaner, haven’t had the issue show back up. But in the mean time, I’ll look into pressure and the spacer thing. 

[cruiser54]

Pressure is likely not the issue. Clutch clearance is the most likely culprit. 

And it may not be an issue now!!  drive it. 

[AZJeff]

I went digging around in my 1990 Jeep Shop Manual, and it says that optimal clutch air gap is 0.016 to 0.031"    Attached is a drawing of measuring the air gap.

[cruiser54]

Thanks Jeff. 

[eaglescout526]

 

8 minutes ago, AZJeff said:

I went digging around in my 1990 Jeep Shop Manual, and it says that optimal clutch air gap is 0.016 to 0.031"    Attached is a drawing of measuring the air gap.

This is good! I guess I could’ve found such too, and good thing I have some feeler gauges.