A/C belts keep breaking

YanMa YatTai · Postby **YanMa YatTai** » Sun Jan 19, 2014 10:41 pm

Just snapped another air con belt today. That's 2 in the last 2 months and the car is hardly used! New belt starts off ok, then begins to squeal only when A/C is on. Squeal gets progressively worse over next few days. Squeals more in higher rpm. Squeal stops immediately when air conditioner switched off. Then suddenly burnt rubber smell in the cabin no more cold air and another belt shredded.

Is the compressor faulty? Clutch? Building too much pressure and therefore resistance on the belt?

I don't think it's simply belt tension otherwise it would squeal when a/c is off too. Right or wrong?

The air con was a complete kit bought and reinstalled into my car.

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MrRevhead · Postby **MrRevhead** » Sun Jan 19, 2014 10:47 pm

Your AC pulley is either wobbling/not par when turned on (at higher RPM) or the tension is too tight IMO.

OMY005 · Postby **OMY005** » Mon Jan 20, 2014 7:34 am

YanMa YatTai wrote:I don't think it's simply belt tension otherwise it would squeal when a/c is off too. Right or wrong?

Wrong, belt wont squeal with a/c off, even though its going around there is no load on it (think idler pulley).

They should last for ages, check the alignment, maybe a spacer is in the wrong place? The manual give specs for checking the tension, they do run tight. Hope this helps.

Andrew

YanMa YatTai · Postby **YanMa YatTai** » Mon Jan 20, 2014 9:21 am

Thanks for replies. I think it would be too loose rather than tight as the squeal is the belt slipping right?

It looks straight when running but will take a closer look at alignment of pulleys.

These belts look like it's difficult for them to jump, but obviously it is somehow.

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Rolley · Postby **Rolley** » Mon Jan 20, 2014 10:02 am

This will be a bit of a novel but I spent a few years with Ford working on Lasers and Capris and this is what I found.
Just to confirm I understand you, if you were to put a new belt on and never turned the A/C on it wouldn't squeal and the belt would not snap?
The problems only start when the compressor is engaged?

If the belt is quiet and does not snap with the compressor off then it says to me the pulley allignment and bearing are OK but it would not hurt to get a straight edge between the pulleys and check everything is square. Also you can release the belt tension and give the compressor pulley a bit of a wiggle to check there is no excessive free play.
If all of that is OK it then points to the compressor taking much more force than is gennerally required to turn it when the clutch is engaged. Because the compressor is now harder to turn the weak spot in the system is the belt which cant transfer the Torque from the engine to the stiff compressor resulting in it squeeling either when it is dragged over the slower spinning compressor pulley or because the crank pulley is spinning faster in the belt slowed down by the failing compressor.

So to me it sounds more like a failing compressor. With THE ENGINE OFF place your palm on the clutch plate on the front of the compressor and try turning it by hand, the belt will hold the pulley stationary you will just be turning the compressor.
There should be some resistance but it will turn by hand. Then if you have access to another MX try turning its compressor and see if there is any difference in the force required.

Next step if there is no obvious failure of the compressor is to get your system pressure and oil level checked. If you are low on oil (A/C oil) or the pressures are too high it can put load on the compressor. Fingers crossed a fresh charge of oil and the proper amount of gas fix it if not I'd be looking at a new compressor.

Good Luck, I hope this helped.

Rolley

YanMa YatTai · Postby **YanMa YatTai** » Mon Jan 20, 2014 5:19 pm

Rolley that is excellent advice and confirms my suspicions. :beer:

Yes, problems only when compressor engaged.

Will do the basic checks then take a look at oil/gas pressure. My suspicion is either clutch needs servicing or there is too much pressure building as you point out. Would the fact that squeals more at high rpm and gets progressively worse over time point to gas pressure too high?

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Rolley · Postby **Rolley** » Mon Jan 27, 2014 5:42 am

That would make me think it is definatly a bearing problem.
So is it the clutch or the internal bearings of the compressor?
If it gets worse hot then I would check how the clutch (pulley) bearings and the compressor bearings feel to spin by hand dead cold with the belts off. Then put it all back together take it for a good drive to the point where you hear your problems starting then pull the belt back off and check the feeling of both bearings again by hand.
Which ever is tighter to turn than your first test is your problem.

Without getting my hands on it I suspect it is low on oil from a system leak somewhere and the compressors internal bearings are binding up as they get hotter during operation.

The clutch is just a big electro magnet sitting on a bearing so if it engauges and the bearing runs smooth and quiet when spun up in your hand with the belts off then it is working as intended.
On 90% of A/C compressors the clutch is a non servicable part and unless you find one on a stuffed compressor it is almost always easier to replace the whole compressor assembly. They are a press fit on to the front of the compressor and without a good bearing puller you really do risk completly buggering the whole lot just trying to get it off.

Good Luck.

Rolley