Rev counter not moving

Slowly getting to the end but still some gremlins.

When the engine is running the ammeter shows a healthy charge but the ignition light stays on and the rev counter refuses to budge off zero.

It’s a complete new loom so no broken wires. Where should i look for the solution

Are running a stock ignition (points) or something electronic?

Im using a stock distributor with points. I think wiring is the same as series 2 for the distributor and ignition light

Test the wires in the problem circuits for continuity. I had a brand new harness where a connector wasn’t making contact with the wire. The insulation hadn’t been stripped back far enough when the harness was made up.

Assuming you have an electronic tach

Power goes into the tach and then to the distributor. Because your engine runs, this wire path is good

There is another power wire to the tach that powers its operation and causes it to sense the ignition pulses. Is suspect you are not getting power to this connection on the tach

Dennis
69 OTS

I ran continuity tests on all the taco wiring and it’s all good but thanks for the suggestion, it’s a good idea to start with basics

Check the voltage on each of the tach connections.
The green wire comes from fuse 6 and should be 12V
Dennis

If the green wire is at zero volts, your tach won’t work

If you find your tachometer is correctly wired, there is an electrolytic capacitor inside that should be replaced.

Thanks everyone for all the info. I’m still working through all suggestions. Does the fact that the ignition light stays on when the engine is running and showing charge have any bearing on the tacho problem?

Measure the battery voltage when charging. You’re looking for something like 13.8 volts. The charging light might be indicating that your voltage output from the alternator is low. When the engine is off the battery voltage should be something over 12 volts.

There should be no relationship between the ignition light staying on and the tach not working
Dennis
69 OTS

Voltages are good both off and running. Could it be a fault with the AW3 unit. It’s a new one but it wouldn’t be the first new electrical item to fail.
I’ll swap it with a spare to see if that’s the problem.

If the tach is nonresponding, I bet the fans aren’t working, either. Fuse 6.

The ignition light is independent of almost everything. It doesn’t even tell you much about the alternator.

Sorry for late reply. Other jag problems took over precedence.
I’ve checked all the continuity and live feed to the tacho but there may be an issue with polarity of the loop around the plastic block.
Next job is to check that. If that doesn’t solve the problem I’ll check the capacitor.

Thanks for the hint.

Kind regards
Alan

I have 12v on the green wire. The engine runs so the white wire loop must be pulsing.
I need to check polarity around the loop, if that fails I’ll look at the internal capacitor.

Kind regards
Alan

Apologies for late reply, lots of other jag issues took precedence
I have 12.4 volts without engine, 13.8 volts with the engine running.
The green wire is live and as the engine is running the white wire must be pulsing.
Next task is to check polarity of the loop and maybe switch over the white wires in the connecting block.

Kind regards
Alan

Sorry for late response, many other jag issues to contend with.
Fuse 6 is good. Frank run. All wiring renewed and continuity checked. Live green to tacho is good showing 12.4v static. As the engine runs the white loop wire at the tacho must be pulsing. Next job is check the internal capacitor.

Kind regards
Alan

When my ignition switch fried several years ago and melted the white wire that loops thru the tach I had to re-wire that section. At first the tach would not work. I fiddled around with the loop and the block that attaches it to the back of the tach and it started working. Not really sure what the initial problem was or how I “fixed” it but all has been fine since. Perhaps it was the same type thing as smacking the TV on the side in 1968 to fix the vertical hold.

David
68 E-type FHC

It was simply a matter of tightening the loop around the pole to ensure that the pulse was strong enough to be registered by the tacho