FredR

Yesterday I was going to take the 928 for a spin, the motor fired up OK and after reversing out of the garage put some more air in the tyres. I was then about to set off and realised something was amiss- the dash panel was no longer working and the turn chevrons were flashing rapidly. Checked fuse 39 and sure enough it had blown so replaced it knowing there was a fair chance the replacement would also blow. The dash was now working but the turn chevrons were still flashing rapidly so I tried to switch on the hazard warning lamp - the indicator lit up in the switch but nothing happened. Turned off the motor and switch back on to see the switch lamp was off but the chevrons were still flashing rapidly.

Set off on a test drive and after about 5 minutes the dash panel went dead again- another blown fuse. This afternoon i pulled the hazard switch from the pod- could not see anything visually obvious. Took a look at the wiring diagrams and could not see anything interconnecting the two systems but my skills with wiring diagrams are limited.

Appreciate any thoughts/suggestions as to what may be going on.

Mrmerlin

while putting in the key you hit the hazard switch ,
try cycling it a few times ,
you might also try a battery disconnect.

gazfish

Maybe try running the car with the switch removed to confirm it is the problem, did you have the switches out recently and might have swapped the connectors?

FredR

Thanks for the inputs- tried all of the above to no avail.

I have had some success isolating the problem this afternoon. It seems the rapid flashing of the turn signals problem is connected to the other switch located above the hazard switch- I disconnected that switch and the mysterious fast blinking of both turn signal icons stopped.

I have not used any of those dash panel switches in ages except the lights on switch and even that rarely gets used.

The hazard switch was not working so I reluctantly pulled that apart knowing ball bearings and springs were going to go twang- managed to catch them all. Have to analyse that but cannot make sense of the wiring relative to the wiring diagram and terminal numbers.

FredR

Well this is starting to look like a farce! I was studying the hazard switch that does not seem to work and the terminal numbers embossed on the switch did not correspond to the wiring diagram- hmm! I took the wiring diagrams into the garage and looked at the cables and the colours did not match the wiring diagram- looked at the wires on the "other switch" and they matched! Seems dipstick here put the switch covers on *** about face last time I had the dash off a few years ago - durrgh!

So, I assume that the switch for the rear screen heater does not work [ I will be checking this with my DMM]. The real hazard warning switch does in fact work. With the ignition on the rapid flashing of the turn signal icons starts- when I switch on the hazard lamp the rapid flashing on the dash panel slows down and the hazard warning flashers on all four corners work. Switch them off and that rapid flashing lamp on the dash panel turns on again. Unfortunately the dash panel gauges are now not working at all and fuse No39 is functional.

Not sure whether that clarifies or complicates matters!!!

Kevin in Atlanta

Be very careful with the rear screen heater switch. If it shorts out it will melt wires from the CE panel to the distributors.

Ask Kevin Wilson. We had to pull the engine to replace that entire harness.

FredR

Kevin,

I am inclined to leave that heater switch disconnected as I never use it anyway

FredR

The hazard warning switch appears to be working exactly as per the wiring diagram schematic.

The rear screen heater switch also appears to be working OK despite what I said earlier- embarassed to say but I did not appreciate it was a rotary switch until I looked closely at the wiring diagram.

As to what is going on I have not been able to fathom out as yet. I will chase out both circuits tomorrow to make a diagram I can understand/test.

Kevin in Atlanta

The hazard switch and turn signals share wiring.

Not sure that adds anything to your problem solving.

FredR

That is precisely why I need to mak a sub system diagram rather than chase my *** across pages of wiring diagrams the majority of which is radar clutter.

It would be useful if anyone can advise why the higher frequency flashing might be taking place- to me it looks like it is being activated by something rather than some kind of fault but until one solves the riddle it is wise to keep all options open.

jschiller

I normally associate a fast flash rate with non-functional bulbs because the mechanical flasher has no load to it from the bulb(s).. Fred, are you sure the lights are actually flashing when you get the fast flash on the cluster?

FredR

Apologies if my description was a little confusing in the midst of my own confusion- the "faster flashing" only happens on the dash display showing the directional icons. This flashing happens when the ignition is switched on. The first time it happened my dash display gave up the ghost after about 3 minutes of driving- fuse 39 [5 amp] had blown. I replaced the fuse and a similar thing happened I assumed the fuse had blown but that was not the case so now I am trying to figure out why the dash display is out.

Mrmerlin

ALERT make sure to disconnect the battery prior to switches removal from the pod,
otherwise you risk shorting a wire back to the CE panel,
NOTE as the switches slide out of the aluminum pod housing,
the side of the switch and the exposed terminals can ground.

You might need to put deoxit 100 on the turn signal switch

FredR

Hi Stan,

I always disconnect the earth strap anytime I want to play with the electrics otherwise I guarantee I will blow something!

Just spent a few minutes on the thing and whilst my head was in the footwell testing fuse 25 [which was OK] I heard a relay clicking at the same frequency as the mysterious flashing on the dash panel when the ignition switch is on- it was relay XIII- the flasher relay surprise surprise. The $64 million question now is why is that thing clicking the way it is? Could it be a relay problem? Maybe I will try my spare relay assuming I can find it.

Switch on the hazard flashers and they work and flash correctly, deploy the turn signal either way that behaves as normal but cancel the signal and the mystery higher frequency flasher comes back into play.

My tests suggest there is nothing wrong with the hazard flasher switch or the rear window defogger switch.

FredR

I managed to dig out my spare indicator relay and try that. For some reason the panel semed to come back to illumination with the digi dash, tachometer, oil pressure gauge all working- the voltage gauge was not working and not sure whether the speedo and the temp gauge would have been working. Decided to take it for a ashort drive to warm things up but no sooner had I left my garage fuse 39 had blown again and the dash was out. Fuse 39 is powered from bus 15 which is live upon ignition on. Now I am pretty sure there is no issue with either the hazard indicator or the rar screen heater power supply. Fuse 39 leads directly to connections 12 and 13 located on plug two of the display. So the problem is likely in the display panel itself. I know that one of the 4 connectors on the back of the panel has one of its locking arms broken- a little problem I inherited with the car. If that connector had worked a little loose I doubt that could explain the symptoms.

So I have a blown fuse 39 [twice] with relay XIII clicking away merrily [only with ignition on] and the flashing icons on the display panel- presumably all caused by a common fault so what am I missing here?