Franks928s

I have a '85 928s and I've recently began hearing extremely loud clicking that sounds almost like a relay thats gone wild. The sound seems to be behind the center area behind the heater/Ac/Radio. I have found that if I move the power slide on the heat/AC unit in between positions, the sound will stop but then comes back on when I hit the next setting. I'm 99% certain the sound is not coming from the heater/ac electronic control unit. Any suggestions?

Thanks!
Frank

M. Requin

Juust a WAG, but listen at the little port for the cabin temp sampling fan- maybe you have something caught in it.

Mrmerlin

from your info you have a leaking vacuum pod in the center console.
there are 2 of them, plus one under the pod for the defrost and them one in the blower box for fresh air open/ close.
If you shut off the HVAC controls it should stop but you need to remove the left console cover to diagnose the line thats leaking.
Wallys tips at 928gt.com will provide details on how to proceed.
The sensor inlet that Martin suggested should be running all the time the HVAC system is on so moving the lever to make the noise stop rules this out. BUT it wont hurt to listen for a noise , to test the fan hold a lit cigarette up to the opening the smoke should suck into the grate with the HVAC system on

WallyP

Use a light to look in the center vent at the comb flap, and see if it is cycling - that is the most common cause.

If so, replacing the vacuum actuator is normally the fix. The HVAC paper in the Tips/Links section of our web site has much more info.

You can plug the orange vacuum line by your right ankle as a temporary move to stop the noise and allow the rest of the system to work properly.

Franks928s

Thanks All! I did remove the center console vent and yes, the flap was cycling! THanks for youar help.

Frank