S60: strange noise behind dash

I own a 2003 S60. It has started making a noise which seems to be
coming from behind the dash. It is a subtle noise which sounds like a
servo motor (almost the same sound as adjusting the rear view mirror
when it it reaches its limit). The noise is randomly intermitant. I
have not been able to link the noise to anything (ie. AC, heater,
zone, ...)

I had a mechanic ride in it today and, of course, the noise was not
present. However, there may be a clue since today is much colder (by
40F) then all the previous days during which the noise was present.

Any ideas?

Thanks,

Andy

 

Is it like a mechanical whirring noise, that lasts for a duration of
approximately 1.5-2 seconds? If it is I have noticed this only my families
1993 960.... it has always been there, I assume it is a normal noise, if it
is the same thing, then its something Volvo has been using for a while now.

We never noticed it right away either, when our car was new the only unusual
noise was a ticking, this was from the valves doing their adjustments as the
engine was being broken in, the whirr was the second noise that was
discovered. Personally I think it is something to do with the power
steering.

Now our 960 makes the whir, some very slight creaks from the plastic bits
over some road surfaces, and the nosies of whatever my dad has put in the
sub-trunk (emergency stuff I guess...)

 

I own a 2001 S80 and my car makes the same noise. Having spoken about a
year ago to the local dealer he said it's the climate control/air-con
shuffling the air vents inside the dash to regulate air flow into the cabin.

 

Makes sence, as all three of our cars have ECC, maybe we should try setting
it off "auto" for the vent direction and see what happens.

 

cabin.

Actually, I think the noise you are likely hearing is the aspirator fan, a
small fan in the face of the dash that brings cabin temperature air over the
thermostat sensor.