Any Electronic geniuses on here ?

[Aidan]

I'm looking for someone who can find the fault on a rev counter dash circuit board I've got, it was working apart from the clock, which I fixed, tested it on a van and all good, but after I sold it on it didn't work properly when fitted by customer, so I took it back and yes it's faulty and I've reached the limit of my testing ability - it's going to be a diode or resistor that's gone I think, or a short circuit, there's no ICs involved , unless all three bod circuits I've got are all faulty with the same fault, but like I say it did work when fitted to another van.
If you can help please drop me a pm or give me a call.
It's a diesel rev counter dash so if it can be fixed it will make someone very happy. There may be more out there that need such diagnostics too, the right person could have a nice little sideline in fixing these if they wanted.
And anyone who could diagnose eber circuits would also be very useful.

[VWCamperfan]

I can test down to component level if it helps. Bit of a distance away though.

[billy739]

is it the clock that is still not working? everythink else ok?

[Aidan]

clock's fine, on its own, but when on a van with ignition feed it doesn't work, and the start up system doesn't work completely, coolant light flashes, but no oil light, no glow plug light when plugs on; it's as if the split tach signal is short circuiting somewhere...it did all work, but I may have fried something by indudicious use of multimeter when testing on bench. All the leds work in themselves, but when connected up to a bod and with correct inputs it doesn't work, it needs testing by someone who can identify the components and anticipate the correct values, and does anyone know what form the tach signal on a diesel is ?

[Syncro G]

does anyone know what form the tach signal on a diesel is ?

I'd have thought it will be a full sine wave as they take the signal off one of the altinator windings. Not sure what peak voltage would be, could be a fair bit (never got round to reading "altinator secrets"). One day I'll borrow my mates Ociloscope and have a look.