MDH

The blower on the engine of my C2 won't stop. Runs all time - I had to dissconnect the battery this morning to stop it. I was going to look things over this evening after work but meanwhile thought I'd throw this out and see if anyone had any ideas. (relay maybe?)

Adrian

At the rear of the blower fan there is a connector in the plumbing. You cannot miss it. Disconnect this plug. This is the temp sensor which activates the additional engine cooling function. It has probably failed shorted. Pulling the connector should stop the fan running. The fuse for this fan is in the engine electrical bay in the left side of the engine bay. The relay is there as well. The additional engine cooling function is controlled by the control unit in the dash.
Ciao,
Adrian
911C4

Randall G.

Hey MDH,

Some thoughts:

-As you suggest, the relay is stuck. The 12V power supply for the rear blower is always-hot. So, if the relay sticks, the rear blower will be powered up, even with the ignition off.

The relay is the same one used for the A/C condenser and oil cooler fans. So, it's easy to check if the relay is the problem by temporarily swapping it with either of the two. The A/C condenser and oil cooler fan relays are located in the fuse box in the luggage compartment.

-The rear blower temperature sensor has failed (as Adrian has suggested), causing the climate control unit (CCU) to think engine temperature is high, running the fan to try to cool the engine.

-The rear blower temperature sensor is loose or unplugged. I'm not sure of the exact logic/sequence required, but myself and several others have learned that the rear blower will run continuously in slow-speed if the sensor is disconnected, ignition off, engine cool. I've gone out and disconnected the sensor, and the fan won't run right away. But, after waiting a while or messing with this and that, the blower starts running. Reference links here:

<a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic;f=3;t=004344" target="_blank">Link 1 My First Post</a>

<a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic;f=3;t=004291" target="_blank">Link 2 (Last Post of First Page, First Post of Second Page)</a>

Finally, I've also read of the CCU causing this problem, but the owner had other problems in this case:

<a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=3&t=004499&p=" target="_blank">Link 3</a>

Best of luck, and let us know what you find.

MDH

Thanks for the replies. When I got home, I reconnected the battery and the blower started right up. So I decided to try the relay swap - put in the oil cooler relay and the blower sat silent. Great, faulty relay - this is easy. But for some reason I decided to put the old relay back in and sure enough, the blower remained silent. I started the car and ran with the heat cranked up to cycle the blower off and on and it works fine (!). I guess this doesn't rule out the relay - perhaps taking it out unstuck it. Hmmm

Adrian

I doubt the problem was the relay. I would say the control unit was stuck in the additional engine cooling mode. What you did was to reset the control unit. I would still suspect the temp sensor because these things are know to go intermittant. The main issue to is to know that you still have this function of engine cooling so I recommend you make some steps to try and reproduce the problem.
Ciao,
Adrian
911C4