R129 strange fan noise

[94mattda]

Hello, I have a 1999 R129 320SL, the air con blows cold and everything regards the heaters and cold air works as it should however every now and then it sounds like the interior blowers have a surge of energy and blow a little bit more powerfully and then settle down again to normal after a few seconds. This happens regularly and I wandered if anyone else had this issue or is it normal?

 

[Wearsthefoxhat]

Mine does the same, designed to get the cabin to the required temperature as quickly as possible and maintain it there.


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[94mattda]

Thank you, it does only do it for a few seconds though!! and more like it’s whilst I’m accelerating?

 

[alabbasi]

If it's happening when accelerating then have the alternator tested , your voltage regulator may have gone bad.

 

[94mattda]

Ok thank you will get that done.

 

[Tattmaylor]

Mine used to do that, but last week I could smell an exhaust or burning smell. Now the air con doesn’t get cold at all and no “surging” noise. Had the MOT today and asked them to check it out. Re-gassed but still not working. They mentioned something about the clutch not engaging(??) but needs further investigation. Any ideas?

 

[Stegel]

There’s a clutch on the front of the a/c compressor that allows it to freewheel when not required. If that’s broken, the compressor won’t be powered, hence no cooling.

I am intrigued by the first few posts, as the blower fan in my 97 SL occasionally “revs up” when I accelerate, and the suggestion that it’s alternator related is interesting - it seems to charge just fine, but last time I was under the car I noticed the through bolts in the alternator were corroding and fracturing the alloy casing. I have a new alternator waiting to go on, so it could kill two birds etc.. There’s also a strong smell of styrene in and around the car quite regularly, so I wonder if that’s anything to do with the alternator fracturing too.

 

[Tattmaylor]

So if I could smell burning…could that be the clutch failing?

 

[grober]

There’s a clutch on the front of the a/c compressor that allows it to freewheel when not required. If that’s broken, the compressor won’t be powered, hence no cooling.

I am intrigued by the first few posts, as the blower fan in my 97 SL occasionally “revs up” when I accelerate, and the suggestion that it’s alternator related is interesting - it seems to charge just fine, but last time I was under the car I noticed the through bolts in the alternator were corroding and fracturing the alloy casing. I have a new alternator waiting to go on, so it could kill two birds etc.. There’s also a strong smell of styrene in and around the car quite regularly, so I wonder if that’s anything to do with the alternator fracturing too.

If the alternator is using the corroded mounting bolts to the engine as an earth return that could be the source of the smell?

 

[Stegel]

If the alternator is using the corroded mounting bolts to the engine as an earth return that could be the source of the smell?

It’s not the bolts that hold it to the engine, it’s the bolts that pass through the whole assembly, front to back, and hold the alternator casing parts together - the fractures run longitudinally from the bolt heads. I wonder if it’s whatever resin they coat the windings (?) in being abraded by a distorted casing causing the smell? It still shows 13.8v when running, but I daresay it may go bang eventually. When I finish the current task on the E class I’ll swap it.