Electrical: Rev counter and clock no power with ignition on

[morsing]

Really weird problem... Clock runs fine until you turn the ignition on, then it gets no power (and rev counter doesn't work).

Before I go out and pull everything apart does anyone have a quick idea if this is just a simple problem somewhere?

Thanks

[morsing]

This is bizarre... The power appears to be there so it must be the ground disappearing to the clock as soon as the rev counter gets a signal. Weirdest thing ever?

Am I right in assuming the power and ground to the clock both go through the instrument cluster? Does this mean something internally has broken?

[Clifford Pope]

I know the two are closely related, because I remember when once installing a tacho in a non-tac car, and swapping from a large clock to a small one, there was a redundant cable behind the instruments for switching them over.

I'd pull the instrument cluster forwards and look for a poor connection. It might be possible to waggle them just from underneath?

[morsing]

Hi Clifford, yes, when you have a rev-counter, the clock plugs into a three-pronged connector where the rev-counter sits.

I've wiggled everything, doesn't help. I had the instrument cluster out a couple of months ago, and everything looked clean and tidy.

I'm dreading the cluster itself has a fault with the electronics I do have a spare one, though, could possibly swap parts.

I would like to narrow the problem down before doing that, though.

[Clan]

I had this problem quite a few times when the 240 was current . i connected a wire to the black wire ( earth wire) of that 3 pin plug on the back of the dash and connected it to a seperate earth on the console , rather than trace it through the circuit board ..