Hi, I have a '90 N/A coupe, Got it for around $200 non-running, I've made enormous progress on the car and it's now very street worthy, registered and driving and the information on this forum played a huge part.
There's one little problem I have yet to figure out, I searched but couldn't locate any mention of anything quite like this.
From the outside, my turn signals work perfectly. From the inside, on the dash, it's a different story. When I turn them on, either side, both dash indicators light up. And what's even more bizare than this, the tach needle bounces to the tempo of the blinker! It's only a slight movement around idle, but as my RPM goes up, the needle jumps around more and more until I shut the blinker off. This is really distracting and driving me nuts. Does anyone have a clue what could be causing this?

 

If the S5 car was wired to the manual, then seemingly it can't happen.

The right turn signal wire leaving the CPU is seperated from the left turn signal wire.

The wires leaving the CPU go to the front and rear turn signal light bulbs and also split off and go to the indicator lights in the instrument cluster.

The left and right indicator wires are seperated from each other in the instrument cluster also.

Are you sure when you signal left that the right are not also blinking?????? If you signal left and only that side is blinking but both interior indicator lights are blinking, then I have no explanation for that other than a internal problem with the instrument cluster.

See the diagrams attached for what I mean.

Is the alternator putting out good 13.5 to 14vdc??? If it's putting out only marginal voltage, that might account for the tach making little movements when the signals are turned on.

The tach and turn signal indicators do share a common ground. It' possible that might be the common denominator. Cars with airbags use ground #1 and without use #3. Just a guess and nothing more. Series five cars only. I don't see how a gnd could turn a light bulb on without power going to it. Slim that its the gnd.

 

And if the dwg is correct, there's another oddity.

There are two round plugs on the back of the instrument cluster. And what's noticable, is that the left signal goes thru one plug and the right goes thru the other plug. So It's not even likely the two wires/pins could touch each other and cause the problem.

I do notice the tach input wire is in the same plug as the input signal for the left turn signal. I wonder if you have this problem with only the left signal?????? And didn't notice that the right does not cause the problem??? Not likely but????

The Tach uses the METER fuse but the turn signals use another fuse...TURN. So the fuse isn't in common. Just the ground for the tach and the turn indicators.

Can't be the outside turn lights fwd and aft because you say they work perfectly (I assume one side does not flash when the other side flashes because you said they worked flawlessly).

Might be someone changed the instrument harness and got ???something wrong. Like used the harness for another series or???

Maybe you can come up with another clue. When you turn/press the HAZARD switch, does everything work normal? All flash? In rythmn? Interior and exterior?
I think you'll go batty working on this one.

 

It's hard to say, this car was worked on in the past by a total idiot. He made some really crappy wiring repairs and managed to break about every piece of plastic trim inside the car. Any mods to the wiring were of the "twist together and tape" style. I had a live wire arcing under the dash & everything, I spent a week just fixing wiring mistakes!

In addition to this problem I still have wipers that only work in one speed (and I bought anothe wiper control module off ebay) and as of the past couple days discovered that the tach doesn't work when it's sufficiently cold outside. It even came with an s4 5-speed with a worn out shifter, tranny mount and a 5th gear that obliterated itself in only 200 miles of driving (got a good used s5 tranny in it now)

I' guess I'll keep tracing wires and see what's happening, after that I might suspect the instrument cluster is at fault. I still have to re-solder the clock and figure out how to replace the broken rubber spacers on that circuit board.
Maybe I'll take a short vid of the turn signal problem once my post count is high enough to let me.
Thanks so much for your help Hailers!
Oh and thanks so much for the diagrams, the Haynes manual I have was based off an S4, and is missing big chunks of info on S5s like a lot of the unique wiring changes, as well as no mention at all of the electrically controlled OMP!

 

Don't you just love the completely uninformed?

My seller is local and asked me to stop by sometime after I had the car cleaned up. After experiencing the results of the work he did, I'll never be seeing him again.

 

http://www.rotorwiki.com/images/6/6c...ngDiagrams.pdf

Google ROTORWIKI and there's a lot of stuff on it like the wiring diagrams above for S5.

Go to the FAQ thread on this site for links to manuals. Look for the FSM. Download the Body Electrical and there is some information on the cluster there.

If the outside lights work as they should, as in only one side of the car at a time, then I'd tend to think it's something to do with the instrument cluster. Oh I really have not much of a clue. It could be some place in the wiring where they spliced in a wire that shouldn't be there.

I can't even figure out why the CD drive on this laptop works no more. It has a light on the DVD door that flashes 24hrs a day if the computer is on. No DVD of any kind works. It does not spin up. I removed the optical drive from the laptop and the *pins* are not bent. Gonna buy a external DVD drive to *fix* it. Some fix. New internal laptop drive cost 169.00. External cost 89.00. Doing nothing cost.......very little. HP Pavilion ZE4900.

Taking a laptop apart is a fun adventure.

 

Well the car works faily well now, aside from some smoke when it's cold, and all the lights work from the outside, but once I fix my daily driver I hope to spend some time to try to make this car somewhat nice. I'll be scouring ebay for random interior trim bits to try to make it look like somebody didn't set off a bomb in there. It looks like the guy who owned the car got pissed off and started kicking at the interior or something. The instrument cluster bezel is held in place by a single screw, all the other mounting points have been broken off!

Thanks for the good info again Hailers!