993 Rear Blower Fan

[Easy_Targa]

When I switch the ignition on from cold the rear fan starts up at full speed. This seems wrong. It doesn't seem to stay on permanently once the engine is started but of course its more difficult to tell whether it is on once the motor is running.
Have looked at the ballast resistor and can confirm that this gets very hot (is this normal?)
Anyone had any experience of this?

[computamedic]

Steve,

There are a couple of possibiliies which come to mind. If the 993 is similar to the 964 there is an NTC temperature sensor in the blower plenum which detects the temperature of the cooling air from the engine. The purpose is to run the rear blower to aid engine cooling if necessary but if the NTC sensor goes bad it's likely that the CCU will default to running the blower. Disconnect the sensor to check.

The other likely cause is that the blower relay has fused it's contacts. You can swap the oil cooler relay (from the front electrical panel) to check it.

If neither of these are at fault it's possible the CCU itself is faulty but you want to hope not.

Dave

[LeoSayer]

Try switching on the ignition with the heater temp set to cold. Does it still blow?

[Easy_Targa]

No it doesn't!! The fan is off at the blue dot but as I turn the temperature up it comes on at about room temperature. Thank you for that but is that good news or bad news? I have eliminated the relay as a possible cause but had barely even thought about the CCU itself.

[LeoSayer]

I think that is normal behaviour then. My 993 behaves in the same way, so did my 964.

[Easy_Targa]

Thanks Leo, you have put my mind at rest. I wonder if any other 993 owners reading this have experienced the same thing. There is loads of info. on the net about the oil cooler fan and air con condenser fan but very little about the rear blower. "993 King of Porsche" is also confusing.

[guards red]

Mine's the same. I've replaced the fan resistor for an unrelated issue and it runs the same.

I don't think you have anything to worry about.

[LeoSayer]

Rennlist is a good resource for this sort of thing:

http://forums.rennlist.com/rennforums/showthread.p...

[Firedamper]

Had been scratching my head why the fan carried on running after my bro borrowed the car so b4 I started a family punch up because he broke it I thought i'd just get my facts right....... Lucky I did! Thanks everyone fears allayed. No probs just turn down the temp control. Of course simple really! Lol pesky Germans.

[Wozy68]

Firedamper said:

Had been scratching my head why the fan carried on running after my bro borrowed the car so b4 I started a family punch up because he broke it I thought i'd just get my facts right....... Lucky I did! Thanks everyone fears allayed. No probs just turn down the temp control. Of course simple really! Lol pesky Germans.

Sorry I had t seen this thread before so could have saved you some worry. It's totally normal as you have found out.

[Timbo_Mint]

See here's me thinking you were a fan of having a supercharger at the rear of the engine. I assumed some people fitted it at the front. Just shows HOW wrong you can be if you make assumptions just from the tread title

[Wozy68]

Wozy68 said:

Sorry I had t seen this thread before so could have saved you some worry. It's totally normal as you have found out.

Damn, no wonder I hadn't seen this thread before ............ its five years old.