The last three times I've started the car, there is a buzzing sound which seems to come from the dash, roughly where all the warning lights are situated. The noise gradually goes away after approximately 30-45 seconds. (It does not coincide with any of the warning lights going out, such as spoiler or brake pressure).

Yesterday after driving to work, I turned off the ignition, and then restarted the car-on that occasion the noise did not occur. So in other words it seems to occur if the car is 'cold'.

Any ideas?...Thanks!

 

solution in the 993 DIY section , regards

 

With a C4 or C4S the brake boost pump buzzes away for the first few seconds after switch on and you may hear it now and again whilst idling. That's normal.

 

Dust in the fan housing on the back of the Heat/AC control console. Console is released by putting coat wire hanger pins in the 4 corner holes, the unit pulls right out of the dash, disassemble the fan clear the dust put back in. I did this and the sound went away for 4 years. Needs it again now.
Andy :-)

 

Andy is correct. The CCU fan is loaded up with dust and lint. It pulls out easy after you press the pins in, then snaps back in place.

 

I agree w/ Andy. The CCU has a fan in back which samples cabin air. The CCU is responsible for a lot of temperature analysis for heating / aircon and engine temp monitoring. It gets dirty and you can disassemble and blow it out. Common problem. Just do a search for CCU repair.

Marc

 

Thanks for all the replies.

I took a quick video this morning on may way to work, sorry about the poor quality, but I think the buzzing can be heard ok, it went away about 15 seconds after the video finished.

Just wanted to confirm you all still think its the Ccu fan.

Cheers

 

Get a Fister Stage III Exhaust! Then you won't hear the buzzing!

 

Ps forgot to mention here is a far more entertaining video (IMO) of my boys watching a993 on YouTube. This was taken last year when I was getting ready to purchase my car.

 

fantastic boys, congrats !!!

https://rennlist.com/forums/993-1995...-993-dash.html

 

Thanks to Geolab for the "cure"! Just this afternoon, my wife asked me "What's that buzzing noise after you turn off the ignition switch", so, (thanks to RL), I told her. Just finished the successful operation and would like to add a precaution:
When pulling off the black hose that goes from the fan to the front of the unit, be careful that the plastic sensor support just behind the front panel isn't dislodged. If it is, you'll need some long tweezers to carefully replace it in the cut-out on the round metal tube that's supposed to keep it in place. Don't yank on it because there's a thin sensor wire attached to it. After cleaning out the rubber tube, make sure the tube is inserted properly over that assembly. Then, re-install the fan to the rubber tube. Ah, "the sound of silence"!

 

Glad it was what we thought. I'd hate to have you go through all that work with no improvement.

Geolab - your DIY was superbly written!

 

great DIY!
Once you get the unit removed the hardest part is removing the two plugs and of course getting the two plugs back in.

My noise has now gone away!

 

So I removed the fan and cleaned it, greased it, but still getting the buzzing noise. Should I try replacing the fan now? Anyone else have same problem?

-nels

 

Over time the fans wear out. Bergville FX makes a Replacement CCU Fan