My cooling fan only comes on for about 10 seconds everytime the temp reaches between the second and third bar. One time it did not even turn on and the engine almost overheated. I noticed the fuse slot #29 on the fuse panel has some discoloration. Is this normal? If not, Where should I check for problems? If the fuse slot for the fan is damaged, can I rewire it to another open slot on the fuse panel? Thanks, John.

88 928S4 Auto, 67000 miles.

 

The S4 and later cars have dedicated power feeds from the battery to the fuse panel (2 fuses, 28 & 29) and on to the module on the front apron under the hood. Do your battery service, and make sure the two red wires connecting at the battery positive terminal are clean and snug.

Verify that you have voltage available at that controller on the front apron. There's a troubleshooting guide in the WSM. Look for voltage at pins 1 and 4 of the connector that plugs in the top of that module. Round connector with the metal retainer tab on it. If no or low voltage at either of those, go back through the fuses to see where there is a problem.

If you have good voltage there, you should be able to start the fans by connecting the two wires on the intake temp switch together. That's the switch right up there on top of the engine intake manifold. Connecting the two wires simulates an engine hot-soak condition, key off. Both fans should run. If only one fan runs, swap the fan connections to see if the problem is a fan motor or a controller problem.

Star with those things and post your results.

 

Jim Bailey reminded me that the hood switch has a safety functio that is there to prevnt cut fingers. You may need to use a tie-wrap to hold the hood switch down while you do your testing.

Thanks to JB for that reminder!

 

I can't find the hood-switch. It's not on the right fender, like it was in my "S".

 

I recently had a similar problem, it was actually caused by the solder in the connector in the fan body melting resulting in intermittant operation of one of the fans. I prised the fan connector open (after removing fan shroud assembly) and resoldered the connector.