wds928

This post could also be titled, RELAYS, RELAYS, RELAYS.

Or perhaps, The Twelve Steps of 928 Ownership...

1. I admitted I was powerless over my 928, that my live had become unmanageable.

(with apologies to other's in 12 step programs)

My '94 GTS sat in the cold garage most of the winter and wasn't driven regularly. I didn't pull the battery, but did drive the car once in a while, but not much. Last winter I drove it more, but since buying a 1992 MBZ 500E, which has become my daily driver, I think the 928 became jealous.

To get to the point, the A/C dash button no longer did anything when I pressed the button and the cooling fans weren't working, plus the foglights didn't work (even with new H3 bults). The cooling fan problem became apparent when the engine began to overheat a bit once I started driving it.

Replace the thermostat and flushed the coolant, but the problem persisted. Finally figured out the cooling fans weren't working at all.

I searched the prior posts, read anything Wally P wrote on the subject and started poking around with the multi-meter. Most writeups had to do with earlier cars or those with the cooling flaps. The GTS doesn't have cooling flaps, just the fan controller, the fan speed amplifier, a couple of temp sensors, the hood switch, some fuses and a relay or two.

I couldn't isolate any particular problems, however one post did emphasize that the battery posts need to be regularly cleaned, as the two fans have direct battery power as a failsafe mode.

On Sunday, I did have some limited success testing the fan controller terminals and found that I had only 3 volts where the WSM said I should have 7 volts. And in pulling the amplifier plug, and pushing it back on combined with standing on my head, I got the A/C switch to work as well as the cooling fans, but only for a couple of seconds. As soon as I switched the key off and then back on, nothing.

So tonight, I go at it again. Before I do anything, I just turn the key on and press the A/C button. Wow, it works, plus cooling fans. But why?

Beats the crap out of me. See the 1st step above. "I am powerless....."

So I remove the spare tire, looseded the battery terminals, got the wire brushes and did a through cleaning of all the terminals. I pulled each fuse and replaced it 3 times, plus the fog light relay and the defroster relay.

I also think the defroster relay also may have something to do with the A/C system.

Anyway, that's all it was. Just clean the battery terminals, even if they look good (mine looked spotless). Same with the fuses and relays. I used two 90 degree picks to pull the relays once I had the battery disconnected. Just pulling them off and pushing them back on a couple of times really, really, really makes a difference.

Now the foglights work, the A/C works and the cooling fans come on (automatically with the A/C and with temperature while idling).

I had done this preventative maintenance a year ago, but didn't really think I needed to do it again. WRONG. This electrical maintenance is essential. The cooling fans didn't work because the fan controller didn't see enough voltage, which prevented the A/C from working.

I am now a believer. The electrical connections cannot be too clean or cleaned often enough. I may do this everytime I change the oil.

rbrtmchl

Two days ago I took my ’91 S4 for a drive. The outside temperature was in the upper 70s. I noticed towards the end of the drive that the temperature gauge was slowly rising. The temp gauge normally reads below the 190 degree line when at operating temperature. On this drive the gauge went slightly to the right of the 190 degree line.

Yesterday I began to diagnose the problem. Since the cooling fans are supposed to run when the air conditioning is on, I tried this and noticed that the air conditioning was also not working. There was no HVAC blower fan operation at any speed, the a/c compressor does not kick on, and the light on the a/c button does not light when pressed. I tried other ways to get the cooling fans to engage, e.g. jumpered the manifold intake temperature sensor, engine running, pressed the hood switch, but still no cooling fans at all.

Last night I found this old thread. wds928 / Bill Sanders mentioned the same two symptoms plus the fact that his fog lights didn't work. This morning I checked and my fog lights also didn't work.

My first step was to clean all of the positive battery terminals as recommended in this thread and also by Bill Ball in a related thread. Unfortunately there was no change, this maintenance did not fix the problem.

Then I also found this comment from Wally Plumley in another old thread:

"X-Relay", which is Relay IV, no longer powers the X-bus on the '86. I have no idea why Porsche kept the "X-Relay" or "ignition relay" terminology, because as far as I can tell, it does nothing except power the fog lamp relay. The circuit is on page 97-237 in the FWSM. I assume that the missing relay means that your fog lamps don't work...

On my ’91 relay and fuse chart the X position relay is also called the Ignition Relay-X.

I disconnected my battery again and replaced the X position relay (the misnamed Ignition Relay-X) and this completely fixed the problem! The fog lights work, air conditioning button lights up, air conditioning HVAC blower works, a/c compressor engages, and most importantly, the two cooling fans operate normally.

Hope this helps anyone else with similar symptoms.