E46 Air con noise

[VanBas]

In my 330ci this morning I put my ac on to help demist the windscreen and it was fine.

After about ten miles I stopped in traffic and heard a wurring/slight grinding noise coming from the engine bay which I'd never noticed before. so I switched the ac off and it stopped. Did this a few times and the same happend.

Anyone got any ideas?

[phumy]

Have you actually lifted the bonnet and had a look, that would be my first thing on the list, you never know you might actually see what is causing it....

[VanBas]

phumy said:

Have you actually lifted the bonnet and had a look, that would be my first thing on the list, you never know you might actually see what is causing it....

Its a good point. But no i havent had chance yet, was on my way to to work, no time. Will do at lunch if i get chance.

[adam85]

I think it is fairly normal to hear a faint whirr from the air con pump, I certainly did on my E46

[VanBas]

OK, just been to have a look under the bonnet and under the car and can't see anything obvious.

I dont have an aux fan in the grill that i've read about in some places so it cant be that. It didn't seem like a normal sound so i'm not sure.

[road_rager]

checking the belt that drives the compressor would be a good first move, the e46 compressor is normally pretty quiet

[anonymous-user]

Could be the compressor starting to go. How old it is the car? Mine's noisy on my B3 so I reckon I'll get it replaced new year.

[Robmilford]

my guess would be the pulley on the tensioner even Though it runs all of the time its not working as hard when ac not in use. Its easy to change the noise could be the bearing

[H6CJF]

Usually this is just a sign that it needs re-gassing. In most cases you can't hear anything untoward under the bonnet as the noise is just transmitted through the pipework.

[tgr]

assuming your E46 has the climate control not the very rare on/off air conditioning...

the way it works is that you set a temperature and the unit maintains the temperature by cycling on and off. Therefore when the aircon is activated the clutch engages - at this point if at idle you should see a brief flicker in the revs as the engine takes the strain and the ECU compensates to maintain revs. Less obvious if it happens while driving although perhaps you would sense the drag.

so the sound could be the clutch engaging.

my aircon groans a bit and occasionally sighs a bit like the noise that fridges make from time to time. Nothing to worry about

'grinding' however sounds bad - that shouldn't happen

compressors need very regular lubrication provided by the oil in the aircon circuit - if you haven't had your system serviced recently I would get it checked out, you want to look for an aircon specialist

hope this helps