VehiGAZ

I knew my cooling fans were running, but not quite the right way. I noticed today while the car was idling in the driveway that they both come on and shut off in unison. No A/C running, cool air temps. The engine stuttered a bit when they engaged. Neither one stays on after shutting off the engine ever - no matter how hot it is (this is how I knew something was amiss).

Based on that, does anyone have a diagnosis? Do not overlook the possibility of PO shenanigans!

Mrmerlin

it sounds like it might be working fine.
The stutter is from the elex draw from both fans starting, you could check the fan connections to see if they are burned or corroded also check the fuse panel for a damaged fuse

mark kibort

you might need a new controller. I know where you can find one.

VehiGAZ

At 928 Specialists, right Mark?

What is the actual part number of the controller? I don't know if I'm finding the right part.

VehiGAZ

I will check the connections, Mrmerlin. Good suggestion!

I don't think the fans are working fine, though. From everything I've read here, I should have one fan cycling on and off to maintain coolant temp, while the second fan should come on when the coolant gets very hot (I forgot the activation temp) and/or when the AC is on. In addition, one of them is supposed to stay on for a minute or so after shutting off a hot engine.

This gets me thinking... The problem for many of us, and for new owners in particular, is that we don't necessarily know that something is wrong with our sharks even when it is! It would be extremely valuable to our community to put together a document that describes how some of the more complicated systems are supposed to work (I'm thinking interior lighting, cooling fans, idle controls, AC/HVAC, etc), then describe the various failure modes, then provide diagnostic procedures on what to check and how to check it. Most of the diagnostic and repair procedures have been written up at this point, here or elsewhere. What's missing (or at least obscured) is the baseline of known proper operation. The proper-op knowledge is generally available here on the forum, but even here, there is always a lot of speculative or misinformed chaff to be winnowed from the definitive kernels. Food for thought...

the flyin' scotsman

My '88 car fans don't run unless engine temp is above threshold and/or the a/c is on.

Both fans are always on or off together never singular.

There does appear a slower/higher speed of the fans when they've been on for a sustained time.........hot summers day and a/c on.

If the above is not normal op then I'd sure like to know.

mark kibort

make me an offer!
Here it is ready for pick and pull

mk

Imo000

So the socondary fan only comes on if the AC is running (compressor clutch engaged) or if the coolant temps are veyr high (how high)?

Alan

In the spirit of winnowing - this is pretty much all chaff...

Don't know where you go this from - both fans (on an S4+) should always do the same thing: both stopped, both full speed or both half speed. Even in the after-running case its always 2 fans at half speed.

After-running only occurs when the intake is very hot - in some climates you may never normally get there, but its possible you may have an issue with just this mode. If you remove the intake top temp sensor connect and short together the connection you should get after-running (but only with the hood closed...).

The only configs where fans operating differently makes much sense is when they are both big (coverage) fans: one as a puller and one as a pusher. Side by side fans should always do the same thing (if not your AC will be hosed).

As to the explanations of major systems operation - I have someting on this but its not finished yet - so far about 400 pages covering lots of stuff - everything you mentioned and a lot more... for exactly the reason you noted - if you don't know how something is supposed to work its not only difficult to diagnose issues its also pretty difficult to ever fix anything (or know that you did...).

For example there are probably only a handfull of people in the world who actually know how the alarm & central locking is supposed to work - Porsche certainly never explained it very well - not even in the internal documents...

Alan

Mrmerlin

like i said your fans seem to be working fine, but check the connectors at each fan, and check the fuses for damage

mark kibort

what is that transformer next to the fan controller in the picture? something for the stereo?

the flyin' scotsman

door bell?

Alan

Its a supressor for the amplifier - it was located there for some models only. So its just an inductor sometimes also called a 'choke' in British English.. unfortunately Porsche seems to have mis-translated this to "throttle" in some instances in the wiring diagrams... (at least I assume its a translation issue unless in German that equivalency also applies) odd!

Alan

Imo000

I had that on the 86.5 parts car too but next to it was the amp.

John Speake

There's a good basic write up of the fan system in the Tech Info for MY 87. On the Jim Morrehouse Tech CDs, available from Roger Tyson.