CmackG

So I parked it yesterday (89 C4), and there was a humming noise -- I thought it might be an oil cooler or something, so I left. When I got back, battery was dead.

So I pulled the battery, got it replaced (dead cell from discharge... alegedly), re-installed, connected the cables, and the fan was blowing still.

It's an interior sounding fan, in the past it cuts on when I turn the key, but now it won't stop.
I tried two fuses and a relay (#1, 39 + relay 14 ) which were front blower, oil cooler fan and Front blower relay, but it still runs.


Any ideas? Sure I could take it to the shop, but where's the fun in that?-- and leaving it anywhere requires me to disconnect the battery. And it's evening now......

C

DarrylH

It may be the little sampler fan behind the $CCU$, under the dash. It'll flatten a battery to "no start" in about 12 hours. It's supposed to run about 20 minutes or so after the car is shut off and then turn off, but there's a goofy failure mode in the $CCU$ that has it continue indefinitely. Found the reference I was looking for:
https://rennlist.com/forums/showthre...hlight=CCU+fan

If not that, could be rear blower fan, which you'll hear from outside the engine compartment if it's running.

CmackG

okay -- so I guess it could be the sampler fan behind the ccu. This morning it was a different fan -- a blower in the rear. There seems to be no fuse that stops it, I have to disconnect the battery. I'll try looking at the CCU this weekend.

Moonraker

The fuse for the rear fan is located in the box on the left hand side of the engine compartment, the one with a cover held on with three screws. It will be either a 30 or 25 Amp type.

964_C2

You can disconnect the rear blower. There is a wire with a connector just to the left of the blower motor that can be disconnected. I have a friend that even took the entire blower out of the car....he has had no problems with it removed.

Lorenfb

Removing the CCU suction fan will reduce the "key off" currrent drain, but generally
not to an acceptable drain (.05 - .07 amps) for a reasonable battery storage life.

JasonAndreas

One thing I noticed with the little fan in the CCU was that over the past 10 years or so a LOT of lint & stuff has accumulated in the little passageway that leads to the temperature sensor and the little fan behind the unit. Mine was completely clogged so I took some compressed air and blew it clear and my fan no longer stays on for very long.
With the rear blower you can disconnect it but you won't get much heat in the car and with the blower just sitting there, blocking most of the air that should be going into the heat exchangers you'll notice that your oil temperature will rise upto operating temperature in 1/4 the normal time. The lack of air moving through the heat exchangers can't possibly be the best thing for your exhaust valves either?

CmackG

So where does this problem lead to? Replacing the CCU, replacing something else? I use the heater on the car, or if I don't use the heater, I'll need to store it for a long time. I'd prefer to drive it on nice winter days...

Lorenfb

You need to check the current drain. If you're absolutely sure that the CCU is preventing
the suction fan from turning-off, you should get it repaired. This is because if it doesn't
turn-off, it indicates that other functions in CCU may not be turning-off causing
an excessive current drain.