Dashboard problem - '94 80 TDi

[shark_90]

I know this isn't strictly S2 related but electrically they can't be that much different...

I've told this story on two different forums so I must be mad to make myself sound stupid on a third.. but I figured there's a lot of technical knowledge around on this forum so it may pay dividends for me to ask here.

Basically I bought an ebay special central locking kit for my 80 and fitted it. But when it came to wiring the power, I was a bit lazy and just stole the constant power from the back of the radio. I wouldn't dream of doing that on a new car, but on an older car I didn't think it'd make the blindest bit of difference.

Since then, the dash clocks haven't worked, although the fuel gauge still does. The two lights that flash when you put the ignition on (brake warning and coolant I think) don't flash either. When the engine is running I get no rev counter, and the oil light is on constantly. The speedo doesn't work and the odometer doesn't rack up the mileage. The temp gauge is also dead.

Turn signals work, handbrake light and glow plug warning all work too.

I have 2 80's so I've tried swapping the dash cluster's around - the one out of the "dead" car works in the other and the one out of the working car doesn't work in the "dead" car, so I know it's definitely something to do with a fuse, relay, or wire actually in the car.

This happened a while ago and when it first happened I think two fuses had blown but I can't confirm as I can't remember. But fuse #14 had definitely gone. I removed my wire taps straight away, and replaced the fuse but the clocks are still lifeless. The coolant and brake warnings did flash sometimes when I started the car, as they're supposed to, but they don't anymore.

Does anyone have any idea what I may have done? I've checked the x-relief relay and I've checked every fuse with a multimeter to double check that I wasn't missing a blown one that looked OK.

Any help appreciated

[S2central.net]

mmm this is an odd one... Firstly I'd recommend the central locking kit from VAGparts.com - its plug and play - but hey !

Looking at schematics now for 1994 80 TDi - guessing you picked the red/blue wire on the main 4-pin radio connector for this permanent feed. That is protected by Fuse 14 (fourteen) which also covers the interior light, cig lighter and vanity lights in the sun visors.

Check that Fuse 14 as it also enters the cluster with a red/blue wire at pin 19 on the yellow connector. This appears to power the digital clock in the cluster and makes its way to the T6g connector at pin 1 where it doesn't connect to anything else. Check you can see +12V there.

All the cluster illumination lamps (including the clock) are protected by Fuse 12 (Twelve) that also connects the voltage stabliser on the cluster, the locator bulbs in the fog-light switches, heated rear window and headlight beam adjuster. This circuit is only active with the key in the 'ON' position. It also protects your reverse lights and the MFTS in the engine bay.

The other component involved in cluster illumination is the rheostat device that is adjusted to make them more/less bright. This device is on same circuit as Fuse 12 and links into the feed from Fuse 14 (fourteen) which only is active when the lights are switched on.

Check also you can see +12V at T6g pin 4 ONLY when the lights are on.

Only other suspects are the light switch itself - verify that the grey wire on pin 58 shows 12V when the lights are ON.

Beyond that you are into the ignition switch and relief relay playing up.

Have you swapped the relief relays over on both cars yet ?

[shark_90]

Your assumption is spot on - it was the red/blue wire that I tapped from the radio power connector.

The digital clock works, so that is receiving power.

I have swapped the relief relays to no avail.

Just reading through your post, I may be picking it up wrong but your post seems to focus on illumination a lot - the illumination of the cluster is fine, it's the actual clocks and gauges themselves that don't work. I have no rev counter, speedo or temp gauge. If I've misread your post then I apologise, but I just wanted to be clear and make sure we were both singing off the same hymn sheet!

[S2central.net]

Doh - thats good and bad then... I'll look at the cluster clock wiring later on. I know the fuel guage is on a separate circuit from other stuff... Will get to the bottom of it - its only wires after all !


Paul

[S2central.net]

Something weird is going on alright.

Tacho (G5) and Speedo (G21) is protected by Fuse 12 (twelve). So is the glow-lamp warning bulb and the reversing lights.

Another things in common with G5, G21 and the water guage (G3) is that they are linked to the mini-check module (J268) on the cluster. If something else in the wiring is causing J268 to be ill that would explain why the problem doesn't seem to be with the cluster itself.

Something you can try is removing the coloured connectors at rear of cluster one at a time to see if the problem is associated with one of them.

T26 is the yellow one
T26a is the is the blue one

G21 (speedo) only uses blue connector
G3 (water) needs both
G5 (tacho) needs both

Perhaps not that meaningful - this is going to be a tricky one to resolve remotely. Can you read circuit diagrams ? This is on a single page of the Audi 80 TDi schematics and I can scan it or send it you if it helps.

Paul

[shark_90]

Paul

I can't really read schematics, never had to do it until now and I'm not brilliant at it. However I know a man who can.. anything you have will be a help I'm sure. I'll drop you a PM with my email address and if you don't mind scanning it then that would be great