Paul Bakker

Hi,
Yesterday I had the little motor replaced which operates my cooling flaps in my '90 S4.
I never saw it operating because the rod was broken.

Today before the first start (cold engine) I took a look at the flaps and they were fully open.
I thought they would close 100% after a cold start but looking at them and my wife starting the car nothing happened....

When I brought my car in the shop I myself had tied the flaps to fully open all the time. Also removed the fuse. I told the guys the fuse was removed, they said it was replaced again but I still have to check myself. Outside temperature over here is 18 degrees celcius (summer here).

Can someone tell me how thes flaps should operate ? When do they open / close ? Is it 100% open or 100% close or does the motor regulate it for 0-100% ?

I already know a lot of you guys prefer the flaps fully open all of the time but I like this little Porsche engeneering and we have cold winters over here. Also know Porsche deleted this function over time.

Any help would be nice.

Thanks,
Paul

ammonman

The system is composed of the positioning motor, control unit with sensors, and the output stage. The control unit next to the passenger seat receives input signals from the coolant temp sensor, the intake manifold sensor, the A/C refrigerant pressure sensor, the transmission fluid temp sensor and the hood switch and then sends commands to the positioning motor to set the flap position and to the output stage to vary the voltage to the fans to control temperature. With the key off, the flaps should open 100%. When the key is turned on the flaps should move to 0%. As the signals to the control unit reach certain limits the control unit will vary flap position and vary the voltage signal to the fans to regulate fan speed. The controller will also allow the fans to continue to run after the engine is switched off if the temp at the intake sensor or cooling water sensor are high enough. The controller has flap position ( 0%, 30% or 100%) and voltage settings for each sensors input values that make up the programming. The WSM has a detailed information and test plan on pages 19-11 through 19-26.

Hope this helps

Mike

Paul Bakker

Hi Mike.
Thanks for your detailled reply. It clarifies a lot to me.
Since the hood swich was "open" because I wanted to look under the bonnet during the cold start this morning is it possible the flaps didn't close ?
Next time I'll crawl under the car to look if they close when ignition is turned on. I understand the car doesn't need to be started to see the flaps close ?
Is it possible they don't close at all when outside temp > 17 degrees celcius ?

Thanks,
Paul

Stromius

I remove the fuse (#24?) and just leave them open. They seem to fail with the control unit. Most seem to do so. I believe the louvers were eliminated the GTS.

ammonman

The hood switch only controls after-running of the fans. If the hood is open the fans will not continue to run after engine shut down as a safety feature. You should be able to open the hood and switch the key to the on position and the flaps should move closed to 0%. After starting the car the flap will stay at 0% until the input from one of the sensors to the control unit tells the control unit that the flaps need to be opened. You can either wait for coolant temp to rise above about +78C or turn on the A/C. Either one should cause the control unit to drive the flaps to the 30% position. As soon as the engine is shut off the flaps should go to 100% (full open).

Any troubleshooting of the system really requires the WSM as the procedures are several pages long.

Mike

Paul Bakker

Hi Guys.
Tuns out the garage who replaced the motor didn't put the fuse back in. I told them several times I removed the fuse but although they told me it was back in it wasn't

Furtheron I had to twist the knop on the motor to get it from a stuck position.

Everything works perfectly now! Thanks for your help.

Paul