Should both electric cooling fans come on when cooling is needed or are they staggered depending on the cooling load?

Only one of my fans comes on. It regulates the temp well below the overheat zone. But it hasn't gotten hot here yet.

 

Yes, both fans should operate together. If one is not working at all try swapping the power leads from one to the other and see if the problem is with the fan or the power leading to it. Most likely one of yours fans is bad. Get it replaced before the hot days come or you could overheat.....A/C performance will suffer also with just one fan.

 

There's a temperature sensor with two wires connected to it on the top and near the rear of the intake manifold. It screws straight down into the manifold, and you can't miss it when you look at the engine. As a quick and easy fan test, disconect the two wires that are plugged onto that temperature sensor and touch them together. Both cooling fans should come on at high speed then.

 

Each fan has a separate fuse (#29 & #30).

 

My mechanic installed the S-4 twin electric fans into my 1982, and they are staggered, as the temperture increases. They have been in my car for a year now, and my car has not gotten close to overheating once. One of the best investments I've made.

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by WallyP:
<strong>Each fan has a separate fuse (#29 & #30).</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Each fan also has its own power lead that runs directly from the battery. If you've wondered what those "extra" smaller cables are back there at the battery positive terminal, they run to the fuse panel, and then forward from there to the controller module in the front apron. Apparently Porsched feels that the cooling fans are important enough to deserve their own dedicated wiring.

Several months ago I had a chance to do some diagnostics on a later S4 with the fans-only-run-occasionally syndrome. A high-powered stereo install had somehow left the wires for the fans loose back there at the battery terminals.

Part of the annual electrical maintenance includes inspect/clean all those connections at the battery. Be sure they really are clean and they really are tight, and coat them with Vaseline when they are secured after the service.

One of our European members wrote about doing some component-level repaisr to the FET module there on the front apron. He was chasing a one-fan-runs problem too. Worth a search if you are comfortable with the soldering iron.

Good luck with your quest!

 

I checked the connection at the fan, the fuses, and did an annual electrical maintenance on the car ( I found an old post by Wally) that includes cleaning up ALL the battery terminals. Between one of these steps both fans now work.

Thank you!! This list is excellent.