Manuel928S4

Hello,

I have been trying to get my cooling fans on my 88 S4 to work correctly because they were turning on with a relay when ignition was switched on. I was following the troubleshooting on the WSM and found that my "output stage" wasn't receiving voltage in pin 4 when I tested with the voltmeter.

Is this a common problem? And is there an obvious reason for why it isnt receiving power?

thanks amd happy new year,
manuel

MainePorsche

Pin 4 at the final stage is current line from CE board. It goes through fuse 28.
Is this fuse OK ?
Pin 1 at the final stage is current line from CE board through fuse 29.

These are the 30 amp fuses that power the fans via the final stage control.

Manuel928S4

Oh ok, there must be my problem. In my car, it seems like the plastic melted and someone put some in line fuse. I will check those connections today.
I dont know what kind of rocket genious "fixed" the electrical problems on that car. Yesterday I removed about 50 feet of cables from an aftermarket cd player I from the car and it had very weird connections.


Thanks!!

MainePorsche

Fuses 28 & 29 get their input from a larger caliber (4.0) red wire. There are no other input or output connections of these fuses. These are solely battery voltage/current though the 30 amp fuse, and out to final stage for the fans. If someone in the past had a mechanical fan motor failure the circuit could have gotten hot. If the plastic were that deformed re-routing through a 30 amp inline fuse may have been an option, but I think if that hot and deformed the FET's and/or other components in the final stage may have been damaged too.

Mrmerlin

remember the reason why the fuses melt,
its because the connections are dirty thus increasing resistance thus making things get hot.
Also check the battery connections at both terminals, the 2 smaller red wires coming off the positive post are for the fans power

MainePorsche

In reading your first post again, are you saying the a relay has been added that switches with the ignition to power the fans ?

Manuel928S4

Ok, will clean the ends with a wire brush also.




Yes but yesterday I put everything back to the stock way and went on with the WSM troubleshooting. I really dislike that kind of "fix" that didnt fix the problem and the sound of the fans never turning off.


Im going to the car now and will post what happens after cleaning and checking everything

Mrmerlin

also make sure the sensor is plugged into the front side of the radiator its under the headlight motor ,
if its off the fans will run all the time the key is on,

NOTE if the temp sensor on the intake is shorted the fans will run,
unplug one of the wire to the sensor on top of the intake see if the fans stop

NOTE if the AC switch is on the fans will run with the key on

Manuel928S4

Thanks all of you!
I just got my two fans working as they should. The problem was in the battery wires. They were very very dirty and heated the in line fuse cable and damaged the fuse. I changed the wires on that because they looked very thin and brittle, cleaned everything and they are working again.
Thanks a lot! My electromechanic (is that how its said in english?) saw the fuse panel and got scared and didnt even wanted to touch because it looked too difficult. So I was on my own.

Manuel928S4

My car's XVI relay socket (electronic ignition system) has a jumper instead of a relay. Its supposed to have a relay, right? Is there an obvious reason for doing that?, other than as a temporary fix if the relay died in the road.
Thanks again,
Manuel

Mrmerlin

please post a picture of the CE panel.
NOTE it might require you to pay 18.00 for the privilege of posting.

Manuel928S4

Ok, when doing the troubleshooting, I found that the temperature sensor was not giving any readings. Is this the intake sensor or the one on the radiator?

Also, I noticed that my A/C compressor stays on even if the ac button inside the car is off. Could that be due to some of the weird wiring in the car?

Manuel928S4

ok, I will take the picture tomorrow morning and try to post it

dr bob

The temperature sensor that controls fan speed (and flap position) is at the left (driver's side on US cars) front bottom of the radiator, into the tank. You can see it with a mirror, back behind the AC condenser. I can see mine looking through the grill in the front of the car.

The intake temp switch top center of the intake manifold is a known failure point if it's had water on it. If you wash the engine and get this wet, you can expect that the switch will keep the fans running continuously, but only after a time period long enough for you to think everything is OK. The corrosion devils are slow, but persistent and determined.