Air Conditioning - can't locate source of loud noise from bearing

[grahamtwatson]

I'm getting really frustrated with this :( - and somewhat poorer! Is anyone a Porsche A/C expert who can give me some advice?

I've got a 2002 996 C2 Cab, and there is a quite loud noise which sounds as if there is a bearing screeching coming from ... somewhere. It only happens when the air conditioning is on, I can start or stop the noise to order with the A/C switch. From inside the cab it sounds like it's coming from the engine compartment, but you can't really hear it well enough to locate the source when you open the engine bay. From outside the car it's much less noticable, and I've been unable to track it down for certain. It did seem as if when the compressor clutch was engaged there was the noise, when it wasn't, there wasn't.

I've just replaced the A/C compressor and the expansion valve (as well as the dryer bottle as I cracked the system). Recharged the system and everything is exactly as before - A/C still works fine etc. but the noise is still there :censored: . Can anyone think what else might be causing this? I'm now assuming that there is some other component which is making this noise and transmitting it through the A/C pipework, but whatever it is has to be something that only happens when the A/C is turned on (i.e. the little A/C symbol is lit on the control panel - it doesn't happen if the system is on without the A/C itself).

The only other thing I can think of is that looking at the workshop manual there a fan attached to the condenser. Does this ONLY come on when the A/C is on, not when the cabin air blower is on? If this could be my problem, the manual says to access it by removing the front wheel, liner and wing support, but it doesn't say which side - unless there are two condensers, one in each wing?

Many thanks!

Graham

[wvicary]

A/C on should also engage the radiator/condenser fans-check them first. Did you check the serpentine belt tensioner and rollers when you had the belt off for the compressor change?

[grahamtwatson]

Thanks - yes, I checked all the rollers, seemed to be fine. I haven't tried running it with the serpentine belt off, which I suppose I could do for a few minutes from cold. I just realised that the noise seems to be related to engine speed, which makes it less likely it's an electric fan.

A/C on should also engage the radiator/condenser fans-check them first. Did you check the serpentine belt tensioner and rollers when you had the belt off for the compressor change?

[Mother]

Remove belt to test and go from there.

[BReyes]

This an elusive sound, or has the unexplained files explained it? :)

Edited August 20, 2013 by BReyes

[fpb111]

Two condensers, two radiators, two fans, two speeds on each fan. one set behind front bumper on each side. Fans come on as soon as you turn air on. Fans run at low speed when engine needs more airflow to stay cool, switch to high speed when things start to get HOT.

[valfam]

did you check the blower motor? I have seen the bushing make noise not all of them have real bearings and if the drag gets bad it will start to blow fuses.

[JoostE]

I saw a similar problem with noise related with the AC.

A quick solution was to fill the system to the max, however that solved the problem only temperarly.

In this case both the front radiators were replaced to solve the problem.

[1dmurrray]

Check the pressure at the high pressure port. I recently overfilled my system and heard a really loud screech after the compressor built up pressure in the system. I think the noise was from a pressure relief valve. In any event, the noise went away after I removed some refrigerant.