AC compressor intermittently seizing up

[UnSafe]

I heard an intermittent squeal at idle from the engine compartment yesterday, while taking my wife's '78 911SC out for a day trip. The AC compressor was stalling in an irregular way, causing the belt to drag. I shut it off to keep from ruining the whole mess. Thankful that I could remove the Targa top, I would have melted without AC or an open top.

So, Where to begin? It wasn't difficult to spin the compressor pulley by hand. It blows pretty cold, but probably not as cold as it should.

This car's a basketcase

[kepperly]

Sounds like belt tension! Put on a new belt ,tension as per spec then try a little "BAR SOAP"

Keith Epperly
87 slant nose turbo look carrera cabriolet

[tcar]

Try belt first.

Could be overcharged (too much pressure), too. Those don't have a high pressure cutoff switch so it just keeps trying to run. Did you just have it charged?

Thirdly, your compressor might be trying to go to heaven.

[UnSafe]

I'll replace the belt and tighten it up more. I estimated the amount of belt tightness when I reassembled everything after the engine drop/ clutch job.

No recent freon additions.

I just started using the AC yesterday, so hopefully it's something simple, otherwise I'll have another 400yd rifle target to hang from the fence.

[tcar]

Be careful, you can get the belt too tight... damage the compressor clutch.

[kuehl]

Originally Posted by UnSafe

I heard an intermittent squeal at idle from the engine compartment yesterday, while taking my wife's '78 911SC out for a day trip. The AC compressor was stalling in an irregular way, causing the belt to drag. I shut it off to keep from ruining the whole mess. Thankful that I could remove the Targa top, I would have melted without AC or an open top.

So, Where to begin? It wasn't difficult to spin the compressor pulley by hand. It blows pretty cold, but probably not as cold as it should.

This car's a basketcase

1) First start by checking the condition of the belt, is it glazed, cracked or loose.
2) If the belt condition is good then possibly you might be seeing "lock up".
The compressor can lock up for various reasons: a) excessive high side pressures which you could have checked with ac service gauges by your ac tech, b) lack of oil flow because of oil losses over the years, c) lack of refrigerant flow which relates to having not enough refrigerant in the system ( low side or binary pressure switch would help) , poor pump capabilities or other problems; the refrigerant carries the oil through the system to lubricate the compressor, d) a tired and worn out compressor

Start with inspecting the condition of the belt first since you don't want to tighten up a worn out belt.

Let us know what you find.

[john walker's workshop]

they seize when overheated. don't use it anymore until you check for a full charge and sufficient compressor oil unless you want to buy a new compressor. may be something else, but best to have it checked out. maybe a condenser fan isn't working. for instance, if you run the A/C with the engine lid open, which cuts off the airflow to the rear condenser, the compressor will start binding, causing the belt to squeel.

[scottb]

He's got a 78 SC, likely with a York compressor. Enough said. Ditch it and call Charlie Griffiths (Mr. Kuehl above) and get a Nippondenso or Sanden. That would be a good place to start. If you're going to get serious about your a/c, you should also replace your hoses with barrier hoses. From there it becomes a very slippery slope.

Have fun!

[Scott R]

Originally Posted by scottb

He's got a 78 SC, likely with a York compressor. Enough said. Ditch it and call Charlie Griffiths (Mr. Kuehl above) and get a Nippondenso or Sanden. That would be a good place to start. If you're going to get serious about your a/c, you should also replace your hoses with barrier hoses. From there it becomes a very slippery slope.

Have fun!

I was going to go Sanden, however to rebuild the York was like $45 in parts, and an afternoon. Works like a champ now, almost no RPM loss afterwards. I purchased parts for a 1980 International Harvester, they used the same compressor.

[pmajka]

is it seizing or slipping, i thought i had a seize...then i sprayed some brake cleanter between the tween places and it stops slipping. (lube on clutch is not a good idear)

[rgmrgm]

have the refigerant flushed. any a/c service center should have the proper machine. compressor may be having difficulty compressing dirty refrigerant. symptoms are, turns properly when first switched on then gradually slows to a stop with belt slipping then squeeling. source of contamination in the system could be from hoses or drier.