w126 - all instruments stopped working
 

I drove about ten miles this morning and noticed that all of the instruments, except the clock, stopped working. The car runs fine and everything else seems to work. I checked the fuses. All okay so I rotated each one. Still no instruments. I also noticed that the big relay was buzzing when I turned on the ignition like a relay was closing all the way. I pulled it out and put it back. Still nothing. I don't believe this relay controls the instruments but maybe I'm wrong. Any suggestions?
Thanks
Dave

Replace the instrument fuse, it's cracked. Looks OK, but isn't conducting.

I'd replace all the fuses, the rest aren't in any better shape (bet they are all corroded, eh?).

Peter

No, actually, I went through all of the fuses a few months ago when I bought the car. In fact, according to the fuse diagram, not all of the instruments are connected through a single fuse.
Thanks
Dave

Hmm... OVP relay gone bad? Instrument panel ground wire off?

This is a new one for me. My TE had all the instruments fail, but that was a fuse.

Peter

Peter,
Just for fun, I did replace the fuse and no luck. That relay I mentioned in the first post is buzzing away. Guess I'll start with that.
Dave

a primary ground is broken
 

The buzzing relay indicates a primary ground is broken; it is trying to back feed. :)
Now, your second clue is the sudden failure of the instruments. :)
The only thing all W126 instruments share is the central ground point. :eek:
Sad to say this ground point is roughly six inches behind the instrument cluster, and can only be reached by pulling the cluster out. :(
You will need the special tools and a large batch of patience, to get the cluster out without secondary damage. :eek:
I would wager that both issues are the same ground lug. :)

Thanks for the tip! I pulled the panel a few months ago to change the temp display. Maybe I dislodged it slightly at that time. I'll check it tomorrow.
Dave

Hmmm
 

Not communicating clearly. :o
The central ground lugs are bolts with hords of Brown wire under them, this is against the engine compartment bulkhead. :eek:
Cleaning, testing and repairing in that area is a major PIA for the best of us, there is not enough space for hands, tools or eyes. :eek:
This ground lug area is known for corrosion... :eek:

possible reason
 

Dave,

Yet another recommendation. The guages on my SDL would go to 0 when I stepped on the brake pedal. I removed all the relays ( around the fuse box), cleaned the pins, and re-inserted. This seems to have fixed the problem. Note, I pulled a silver relay that is a shade more to the center than the fusebox. It had a 10 amp blade type fuse on the top of it with a plastic cap. The fuse was loose in the metal knotches that held it.

This may not help but is quick and easy to try. Good luck.

Chuck

I have found that when my key switch returns a little too far counter-clockwise, all my instruments go dead. The car still runs though, it's just the instruments.

Hmmm
 

Will try to get with you this weekend on this issue.

I return, hat in hand. Despite checking, rotating, examining, removing, all the fuses, and worst of all replacing the WRONG fuse - guess what - it was the number 6 fuse. UGH!!! Of course, I discovered this after I removed and replaced all of the relays and removed the instruments to check the ground wires.

I followed the suggestions in the order of easiest first, since I had already checked the fuses-right. Started the car and played with the switch,no joy. Removed all the relays, checked and replaced, still nothing. Pulled the dash, in record time, all ground wires clean and tidy. Went back to the fuses. This time when I pushed them around I saw a little spark on the number 6 fuse. Replaced it and back in business. Sure enough, when I pulled it out this time it fell apart. I'm still concerned about why it blew.

Anyway, thanks for all the help - I'm ready for my dope slap.

Dave

Doh
 

Hello Dave
You beat the bug.
Glad you found and fixed the problem... :D

Enjoy the goofy Homer isms. LOL :D
If something is too hard,give it up. The moral my boy is too never try anything

http://smacie.com/randomizer/simpsons/homer.html?Homer.x=62&Homer.y=73

Happened to Richard Dreyfuss in "Close Encounters"...
 

open your sunroof and see if the Mothership is hovering above. Use sunscreen first.

You didn't perhap use one of the ancient spare fuses in the fuse box to replace #6, did you?

They get old and oxidized (the fuse material is aluminum or copper foil) and crack. The crack is often not visible until you remove the fuse, and even if not used, they go bad sitting in the fuse box.

You are hardly the first one to do this. At least you didn't do something drastic like replace the engine to fix a leaking hose or anything....

Peter