Whirring/buzzing sound behind the hu-803

[barrysharp]

During my XC70 tour about Sweden/Norway after pickup from Goteborg/FDC I noticed that after switching the engine off there was this whirring/buzzing sound coming from behind the HU-803 unit. I have the same unit in my S80 and it does the same and hasn't bothered me until now having also heard it in the XC7.

What do you think causes it do you suppose. I do belive it stops after a while as when I return to car some time after there's no such noise.

BTW I always have CDs in the HU-803's 4-disc changer -- maybe not all 4 but one or more. My sense is that the CD is spinning and after engine/iginition shuts off the CD disc takes some time to spin down -- could this be it ?

One last point unrelated to whirring/buzzing sounds is that the HU-803 unit can become extremely hot -- I say hot as its forward facing surface temp is very much more than just being warm -- it's more like heat one finds in the engine bay after a run http://xc70.com/iB_html/non-cgi/emoticons/sad.gif

Thanks.

[purush]

My car has a HU-613 and I too noticed such a noise.  While it is clear it is some kind of a fan I initially thought it could be the turbo.   I was told by my local dealer that there are one/two fans that cool the radiator and that is what makes the buzzing sound.

purush

[Hiro's XC]

It's not a fan on the 613. There is no cooling fan. One thing to consider is the Iq system on the interior ventilation opening and closing the system.

Jason

[purush]

Jason

Please reread my message.  I did not say it was the fan on the 613.  I said that I have the same noise inspite of having a 613.   The noise is clearly from some fans beind the radiator, which is what you are saying too.

Purush

[wiz]

What? You guys don't have fans on your HU-613's? I got one on mine! http://xc70.com/iB_html/non-cgi/emoticons/biggrin.gif http://xc70.com/iB_html/non-cgi/emoticons/wink.gif http://xc70.com/iB_html/non-cgi/emoticons/biggrin.gif

I heard the fan for the first time in a long time on Saturday. The first warm day we've had in many, many months.

[barrysharp]

According to my service dept this noise is caused by the aspirator fan. This is a small fan that's employed to sense the moisture level in the cabin and is in some way connected to the system/logic that activates the A/C blower after some 50 mins or so after switching engine off to evacuate stale air/moisture http://xc70.com/iB_html/non-cgi/emoticons/smile.gif

Since posting I have monitored this on my S80 and find that the purring sound I mentioned will persist for 1, 2, and maybe 3 hrs. Also, leaving it overnight I'v noticed the purring sound vanishes. I believe this confirms what my service dept described the noise as being.

Also, if after turning engine off, you place your thumb over the temp sensor opening in the central facia below the radio the noise should lessen considerably after a few moments as the sensor cannot do its job http://xc70.com/iB_html/non-cgi/emoticons/wink.gif -- so remove your thumb and let it be http://xc70.com/iB_html/non-cgi/emoticons/smile.gif

[lausch]

Barry, I believe your service department's description is covered in the owner's manual.

[Hiro's XC]

Look,

I was acused of not reading the post earlier. I did. The fan noise is the cooling system coming on aprox 45 minutes after use of the A/C to make sure the evaporator is dry. What was mentioned first by Barry is a sound fron the dash. Not the engine compartment. It is possible that the 813 has a seperate cooling fan. I don't know though. I don't own one.

Jason

[barrysharp]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Support Vehicle @ May 01 2003,06:23)</td></tr><tr><td id="QUOTE">Barry, I believe your service department&#39;s description is covered in the owner&#39;s manual.[/QUOTE]<span id='postcolor'>
The manual describes the A/C blower activating at some 50 odd mins after engined turned off.

The noise I&#39;m referring to is a purring noise immediately after turning the engine off and one that comes from behind the radio facia.

There&#39;s a small (presumably) aspirator fan behind the radio facia (unrelated to Hu-613 or 803) that draws air thru the 3 slotted vent under the radio face. The purring noise is, according to my service dept, coming from this fan that continues to run for several hours after car&#39;s engine turned off.

I hope this clarifies things for you.