Rev counter antics

[DaveB]

It's been a long while since I've been on the forum but I still have the Stag (SOL) and generally it's been behaving itself. However today the rev counter has started playing up very strangely.

When the ignition is switched on the rev counter needle jumps to about 1400prm and stays there; then when the engine is started and at idle the needle goes to max and stays there. The car starts and runs fine otherwise. It's a Mk2 and I have had electronic ignition fitted for over 10 years with no problems.

Any thoughts appreciated, cheers, Dave

[Andrew S]

Hi Dave
How you doing?
I think the reg counter is in the save wiring line as the coil so, could possibly be linked. Do you have or can you borrow a coil to swap over as a test?

[DaveB]

Hi Andrew,
I'm good thanks, how's you?
I've already tried my spare coil, no difference.

[Andrew S]

I’m fine thanks, keeping the yellow sunshine going.
Ok so you have tried that.
I wonder if you can test the rev counter with a direct 12v feed bypassing the ignition to see if the needle flicks up and then you would know it just the dial issue and not in the wiring loom and nothing to do with the car

[DaveB]

Thanks for that Andrew, I'll take a look tomorrow.

[Wheelz]

If the rev counter indicates before the engine runs then
1. There is a fault in the rev counter
2. Something is creating an electrical noise that is being picked up in the ignition circuit (white wire). If you have electronic ignition remove the power to it and see if the problem goes away.

[DaveB]

Thanks guys,

If I disconnect the electronic ignition at the dizzy I get the same problem,
If I disconnect the coil, the rev counter does not react with the ignition on,
With a 12v feed direct to the rev counter I get the same 1400rpm reading.

Beginning the think it's probably an internal rev counter fault.

[richardthestag]

starting to sound like it.

Test the gauge with a nice clean feed from the battery (to replace the green wire connection) and a signal wire (white/slate) to the negative post on the coil.

green wire on the back of the tacho is the supply, white/slate is the wire that senses the speed of triggers the distributor is sending to the coil.

if it is still random then I might be thinking Haunted or buggered

[Goldstar]

I’ve got a nice one in the shed if you need one Dave

[DaveB]

starting to sound like it.

Test the gauge with a nice clean feed from the battery (to replace the green wire connection) and a signal wire (white/slate) to the negative post on the coil.

green wire on the back of the tacho is the supply, white/slate is the wire that senses the speed of triggers the distributor is sending to the coil.

if it is still random then I might be thinking Haunted or buggered

Many thanks, tried a fresh 12v supply and neg, and swapped the electronic ignition module for the spare, still the same so looks like the rev counter is buggered !

[MandM]

Hi Dave glad you are ok , not seen you in a while. we have not been far in ours 149mile between oil changes last year, hoping to get out more this year, might bump into you somewhere

Martin & Monica