Alan

Herman Plug 1 on the controller is what drives the final stages and supplies power to the controller - so disconnecting that makes sense it would stop the fans.

Fuses 29/30 are in the main fan supply circuit before the final stage so those can be used to stop the fans too, but they are obviously good...

I assume Fuse 36 is OK - that feeds the fan controller with an ignition switched supply on Plug1.

Test the voltage on pin S22 or D22 on the central electric panel plugs - this is your trans oil temp switch & Intake temp switches - should be @ ~ 12v.

Alan

dr bob

I think you are referring to the safety switch in the compressor coil circuit. That's on the bottom of that tubing manifold. The pressure transducer is the little can on the top of that manifold, and is used for the fan speed control only on the GTS. On the earlier S4 cars, it also contributes to flap poaition in the grill.

Alan

Dr Bob - on a late 93 and on GTS the switch (both or all three depending how you look at it) is at the top of the Dryer next to the HP fill valve - its configured differently than on an S4. 92's & early '93's are as you describe.

There is no pressure transducer on these GTS's just an additional pressure switch in the combo switch.

I think Herman already found it - now just needs a bit of testing...

Alan

Herman K

Thanks everybody I’m glad to say the problem is gone. I followed all recommendations, did the WSM procedures and they all checked out ok.
I than removed the hood switch for a close up inspection and I found that the slide on wire/connector was loose.
The connector has two slotted ears that slide over the extended parts of the switch body to hold it in place. One of the slotted ears had lost its tension and made the connector loose its grip.
I wrapped them with electrical tape and secured that with a wire-tie.
I really appreciate all the efforts to assist and hopefully this information will help some body else at some point and time in the future.

94 GTS 5 spd

fraggle

bugger you're right - sorry it isn't the TEMP][ on the intake, it was a "thermo-switch" or something along those lines. I didn't replace the sensor in the bridge when I fixed mine.

Glad it all worked out here!

Alan

Humm... its nice when things work - however I don't think this was your problem...

The hood light/alarm switch turns the fans off whenever the hood is open (safety) - but it does not ever turn them on. So if this switch was faulty - by fixing it your fans will now go off with the hood open - but it should not change anything in the behaviour when the hood is closed....

If the other symptions went away maybe it was something else you did - wiring/connection/etc...?

Alan

Herman K

In addition to working the switch I also removed and cleaned the plug on the stage controller. The wire going into the plug had some sharp twist in them and I kind-of straighten them out? All the symptoms did indicate a ground out somewhere. I agree I'm still somewhat puzzled.

Herman K

Alan thanks for challenging my mind on this one! As per my previous post #22 and your #21 I felt obligated (because of the time all you guys spend on this) to try and replicate the problem.

In order to be clear let me recap the events;

1. The problem was cooling fans come on and run at full speed when the ignition is turned on, they’re off with the ignition off. (Engine temperature cold, Houston weather @ 65F)
2. Followed all RL recommendations to fix the problem, results negative.
3. Swap Fan controller and stage speed controller, results negative.
4. Last night I found (so I thought) a loose connection on the hood switch, fixed that but also did another procedure as per WSM section 19, page 25 “Function-testing the output stage, removing the out put stage plug connector and >>> turning the ignition on and off <<< while the cable was disconnected from the stage controller, results positive, followed by a test drive to bring the engine up to temperature etc.
5. Posted #22 on RL indicating that the fix was the hood switch, well Alan did not buy that and expressed his doubts on this.
6. His doubts and in appreciation of everybody else their time to try and solve this problem spurred me on try and replicate the problem this morning.
7. I swapped back (remember overnight the engine was now cold again) the stage controller to the original unit. Turned on the ignition and everything appeared to be ok, went for a test drive and the moment the temperature got to around 175F (about 2-3 miles from home) the car almost died and went in a limp mode. I made it back swapped the stage controller (turned ignition of and on) and everything was fine.
8. Therefore I now believe that when the original stage controller went bad the fans where set to an always on mode and this was memorized until I did a “RE-BOOT”, (ignition on/off) with the stage control plug disconnected
9. Ones the reboot was done (memory erased) and the replacement stage controller was connected everything works as it should at 175F engine running for a while when parked the fans come on in the first stage and when the A/C gets activated immediately go to full speed and when driving in 65-75F weather they are just off as they should be.

Well I hope this is useful information to have available if you run into the same problem. Thanks everybody and a special thanks to Alan to challenge me on this one. BTW Alan let me know if you agree on this one.

Happy 928 motoring to all, keep’m rolling

94 GTS 5 spd
Greetings from the Hermanator

Alan

Herman - I don't know if that "reboot" phenomenon is the way it works - but I like this idea of yours better than the hood switch anyway .
I just hope thats it and it doesn't come back...

If so I'll remember your idea in case it ever happens to mine...

Alan

Herman K

Alan - The following comments are from Dr Bob in regards to my post about RE-Booting, I know he's right but so far things are just fine. I will in time take the replaced stage controller apart as per Nichols repair tips site and see what we find than.

Thank again for your help.

94 GTS 5spd