screaming noise when started

[stonewall]

I started the car today and a screaming noise from under the bonnet started. 2second later it stoped , turn the ac on but only warm air. When i switched it off the noise started again. if the heater is on very low the noice go's. but not every time i start the car up,will the noise start .what could this be thanks for looking at this

[johnnyroper]

Sounds like a problem with aux belt area, knackered belt,seized part.

You need to get belt off and have a check of tensioner,pas pump,alternator (not sure if the petrols has clutch type pulley) air con pump. Make sure air con free wheels with no power,but when you turn the clutch part that also turns all be it with some resistance.

[brianh]

Don't think the petrols have the clutch type pulley on the alternator, The tensioner should be able to be pushed back with a 15mm spanner to release the tension. I'd suspect either the tensioner itself is stuck causing the belt to slip, or either tensioner pulley or idler pulley on the aux belt is failing.

On the mk1 both of those pulleys (not the retaining bolts though) are the same, and you can use the idler pulley to replace the tensioner pulley if the bearing in it has failed. I've not gone far enough into the mk2 to tell if that's the case, but i'd suspect it is (the tensioner pulley isn't available separately from most places, and comes with the tensioner).

Otherwise it may be that the a/c pump has seized - Having a look under the bonnet should give you a clue if thats the case (I'd expect you to have noticed the belt smoking if that was the case though).

[stonewall]

Belt seems fine it only seems to start if the tick on the heater or eon is switched on

[johnnyroper]

Suggests a compressor issue to me if it only happens with econ on,bearing issue with the free wheeling hub? Try some wd40 aimed at compressor see if it changes it,obviously not a perm fix but will give you an idea of it is at fault

[brianh]

Can you see if the centre of the ac pulley is turning (the outer bit will always turn with the engine, the spindle will move only when the clutch engages it).

Did you try the tests Johnnyroper posted earlier?

I'd agree the compressor sounds at fault, might be worth having a look round it to see for any traces of bright yellow dye, There should be some oil in the a/c circuit to lubericate the compressor, though if its leaked out and then seized i doubt adding oil (via a regas) would be enough to make it work again.

[stonewall]

First thanks for the help. Went to the garage today as no luck with WD . Was told its the bearings on the  compressor. And it will cost Ã,£700 to fix. Or just leave it, and just use the heater in winter. and open the windows in summer

[johnnyroper]

Look for a 2nd hand compressor bound to be some in breakers yard,then it will just be labour to swap over and cost of regas. Far cheaper than Ã,£700

[christiant]

Does anyone know if the ac compressors are interchangeable with other VAG models? Are climate control ones different than just AC?

[brianh]

Theres two different compressors shown on microcat against the 115bhp, either YM2H 19D629 BA if built before March 2002 or 6M2H 19D629 AA if later. Doesn't appear to be any difference over climate control or otherwise. It also appears the diesels all use the same two compressors.

It may be worth giving yours a gentle cleaning up and see if you can find any other part numbers on it once you do?

[gregers]

i seem to remember when mine made this horrible noise it was the aircon clutch failing.mine had worked loose bounced about on the spine and fell off into the undertray,i obtained another compressor and with 1 person working from underneath and myself working from the top of the engine we managed to replace the clutch insitu without the need to remove everything and regas.