Hi all, my instrument cluster out-of-the-blue developed a strange issue the other day whilst driving when I turn on the lights, and hence activate the cluster back lighting, the speed /tacho go to zero and the temp and oil pin to max (which was alarming the first time it happened!).

I have investigated the cluster and can find no breaks, visible shorts or tears in the circuit board, and all the warning lamps and gauges work perfectly when the lights are off (I installed a new tacho and temp gauge as part of a refurb last year) so they are all adequately grounded, I tested each back light/lamp and all work. The centre console back lighting works as normal, and the fuse (8) is also fine. Im at a loss, anyone had this issue? It sounds like some kind of short but I cannot find any issue on the cluster/printed circuit itself.

 

I’m betting you have a bad ground. Run a redundant ground to the cluster.

Cheers
DD

 

OK will try that, thank you. Weird that it just "happened"...!

 

Thank you Doug, you were exactly right. It's a mystery how it should suddenly have "lost" its ground, I put a redundant ground fixed it.

 

Matt,

That's quite plausible. It only needs a slight deterioration through gradual corrosion buildup for the earth circuit to start to lose its continuity. Then one day, it's deteriorated to the point where, electricity, being the clever thing it is, has found an alternative easier earth route through another instrument or part of the circuit. Hence, why it suddenly affected a couple of your instruments.

Paul

 

Paul, well said. Very clear and concise. The same principle can occur anywhere there is a poor ground, causing all kinds of weird maladies, especially in lighting around the car. Electricity will find a path to ground, no matter how torturous.
Jon