AC clutch issue

[BLIMP]

Friday I had an issue pop up in the 72 Monaco wagon. Was accelerating from a corner at normal operating temperatures when I heard a slight chirping noise. Lasted maybe 5 seconds at the most. First thing that popped into my head was that it sounded like maybe the water pump bearing was beginning to go out. Then a minute later I began to get a burning wire electrical smell. Immediately I pulled over and turned off the engine. As I did, a decent sized cloud of smoke came out of the cowl. I released the hood mechanism, ran around the front, lifted the hood to see the AC clutch sizzling and smoking. There was some stinky black goop dripping from the end plate. I don't think there was a real electrical wire issue/fire, as the smoke coming off the clutch had a terrible acrid smell.

I let it sit for a few minutes thinking about what I might be. After a bit, for good measure I unplugged the wire going to the clutch and restarted the engine. All seemed normal, no more smoke or sounds. I drove another 10 miles home without a problem.

At the time this happened, there was not a charge in the AC system, nor did I have the fan or AC system in the "ON" position. Although, a couple days beforehand, and 50 miles ago, I had attempted to recharge the AC system with 134 after installing a brand new drier. For reasons that I had not yet resolved, the system didn't seem to work. So I vented it again in the preparation of installing a new evaporator.

Not sure if fiddling with things would have caused this issue. Nor do I even understand what the problem is yet. There doesn't seem to be any slop or play as if there is a bad bearing.

Does anyone have any advice or ever had a similar experience? I'm going to go flip through the FSM but merely thought I'd ask first.

Paul

 

[Davea Lux]

Put a socket on the clutch mounting bolt and see if you can turn the compressor over by hand a full revolution. I suspect that your compressor has seized and is smoking the A/C clutch. The clutch should not be engaged with the system in the off position, so you may have a wiring issue, such as a short or a fused relay that is allowing power to get to the A/C clutch. You can check this with a test light to the disconnected wire from the A/C compressor. As the clutch assembly stopped smoking with the power disconnected, I do no think the bearings in the clutch have failed.

Dave

 

[BLIMP]

Thanks Dave I will check those things and report back

 

[BLIMP]

Well I loosened both belts. Clutch seems disengaged, pulley spins nice and free, no slop or binding. Put a 1/2" socket on the center bolt. Turning it clockwise...nothing, nothing...and I stopped for fear of snapping the head off. Put quite a bit of force on it and it didn't budge.

 

[Davea Lux]

The compressor is toast. Before you install a new one be sure to locate the cause of it running with the A/C switch off. When a system is out of refrigerant, the oil for the compressor all gets pumped out into the rest of the system and the compressor starves for oil and burns out.

Dave

 

[BLIMP]

That darn compressor sounded nice and quiet a couple days ago when working on it...guess I should have left it unplugged as a safeguard after I vented the system.

What a damn shame, thanks for the advice Dave.

 

[Yatzee]

Friday I had an issue pop up in the 72 Monaco wagon. Was accelerating from a corner at normal operating temperatures when I heard a slight chirping noise. Lasted maybe 5 seconds at the most. First thing that popped into my head was that it sounded like maybe the water pump bearing was beginning to go out. Then a minute later I began to get a burning wire electrical smell. Immediately I pulled over and turned off the engine. As I did, a decent sized cloud of smoke came out of the cowl. I released the hood mechanism, ran around the front, lifted the hood to see the AC clutch sizzling and smoking. There was some stinky black goop dripping from the end plate. I don't think there was a real electrical wire issue/fire, as the smoke coming off the clutch had a terrible acrid smell.

I let it sit for a few minutes thinking about what I might be. After a bit, for good measure I unplugged the wire going to the clutch and restarted the engine. All seemed normal, no more smoke or sounds. I drove another 10 miles home without a problem.

At the time this happened, there was not a charge in the AC system, nor did I have the fan or AC system in the "ON" position. Although, a couple days beforehand, and 50 miles ago, I had attempted to recharge the AC system with 134 after installing a brand new drier. For reasons that I had not yet resolved, the system didn't seem to work. So I vented it again in the preparation of installing a new evaporator.

Not sure if fiddling with things would have caused this issue. Nor do I even understand what the problem is yet. There doesn't seem to be any slop or play as if there is a bad bearing.

Does anyone have any advice or ever had a similar experience? I'm going to go flip through the FSM but merely thought I'd ask first.

Paul

Just went through this same situation on a 66 Imperial. It turned out that the clutch bearings were toast and seized when they got hot. The bolt is left-hand thread. The smoke comes from an over heated clutch assembly (450 degrees plus) roasting the underside of the drive belt. Remove and replace the clutch before tearing the compressor out and you may save a bunch of cash. RV-2 compressors are built like Sherman tanks and when they start to go they knock and rattle like crazy. This 66 was the second car I came across that had the compressor running all the time so I assume the interior control panel was the issue. As a quick fix, an illuminated rocker switch was wired into the power circuit to the compressor clutch and mounted inside the car. It was reported that the mileage on the car went up by 3 mpg when the compressor was not in use.

 

[Davea Lux]

That darn compressor sounded nice and quiet a couple days ago when working on it...guess I should have left it unplugged as a safeguard after I vented the system.

What a damn shame, thanks for the advice Dave.

You can try removing the clutch to verify that the bearings are not seized. Nearly always if you can turn the clutch pulley with the belts off, it is the compressor that has failed.

Dave

 

[FURYGT]

Keep in mind that the A/C compressor clutch engages if you put the HVAC control on defrost. If you selected defrost while you were driving that could be why the clutch engaged. Just a thought.

 

[CBODY67]

ONE thing, on the '72 C-body cars (manual a/c, not ATC), the a/c compressor runs ALL of the time, even with the "OFF" button pushed in. The fan also runs at a very slow speed, with the "OFF" button pushed in. Something about keeping the system dehumidified in humid conditions? But that's the way our '72 Newport was from new. When you move the heat lever to the right (cable-controlled water valve), you can hear and feel a "click" about 1/2 way toward the max heat position. THAT's what turns the compressor off. Easy to reposition the cable so that the water valve is "off" when the lever is just past the "click", but it looks funny to see the heat lever 1/2 way "hot".

IF the clutch was actually slipping, don't even consider reusing it. If the compressor's bad, get a new compressor with clutch already on it. Usually cost effective to do it this way, too.

The clutch is metal-to-metal, so when one side slips, the other side is eroded, which compromises the friction interface a good bit. Went through this on my '77 Camaro with an A-6. I put a new clutch on it, then did the "break-in" procedure of clicking the clutch on and off about 20 times so the new side would become seated-in with the existing side. After dark, a "sparkler show" as the new piece wore against the old existing piece. That's when I noticed how rough the existing side of the clutch was!

If the a/c compressor is trying to lock-up and not rotate, the belts will begin slipping and start to melt.

Was your system already changed-over to R-134a? WITH compatible oil in the system?

IF the system had no gas in it, the "low pressure switch" should have kept the compressor from running at all. That switch is usually on the receiver drier on Chrysler products. Not sure why the compressor on a '66 Imperial would run with the system turned "off"? Our '66 Chrysler didn't do that.

The reason I found out about the "full-time compressor" was in trying to get the '72 400 to run as good as our '66 Newport 383. Getting the compressor to not run helped that a bit.

CBODY67

 

[Yeahrightgreer]

Even though this wasn’t an actual “fire”, this is why we all need - especially us older car guys; a fire extinguisher equipped somewhere in the vehicle.

I’m glad once you checked under the hood it wasn’t heavy smokes or fires. I’m sure my heart would be pounding like a hummingbird.

 

[BLIMP]

Tons of good info guys, thank you all for your comments.
Let my situation be a lesson for anyone out there contemplating recharging AC on your own. Do it incorrectly, and it can turn into a fiasco. I've been searching this forum for information and watching videos on youtube. Went out and bought a vacume pump, gauges, new drier, expansion valve. Pressure checked the system with Nitrogen. Long story short, at a minimum I'm going to need another compressor and a clutch.
I've put a decent amount of miles on the wagon this summer, and the clutch hasn't been engaged or cycling. All the dash controls have been in the OFF position. And yes it was a huge relief to not find a fire when I lifted the hood, very scary stuff. Will be buying a couple extinguishers soon. Thanks again.
Paul