Rev counter wiring /coil

[Skeggybloke]

Don't no if any one can help , had to try a different coil on the excel se due to probs with running but turned out not to be that so old coil put back on , the rev counter isn't working and I believe this if feed by the coil

Can any one let me know how the coil should be wired so we can check we got the wires back on right way round
I have two white wires each going to a connector and two wires joined together in one connecter , which one goes to rev counter ? And from which side of coil ?

Cheers

[fueltheburn]

Most rev counters work off the negative side of the coil. The end of each spark cycle is translated to engine speed.
The two white wires should be positive/ignition if memory serves.

edit: - 2 white wires to positive side of coil.
- The white/blue and white/black from neg side of coil. The white/blue goes from neg side of coil to tacho.

hope that helps

[Skeggybloke]

Thank you for the answer I will have a look in morning and check it with luck it will get the rev counter working again

[Skeggybloke]

Ok I have had a look all wires are right even checked northing had fell out behind dash is there anyway to test a rev counter ?

It was the rev limiter that has failed but can't see that stopping rev conter working unless I have missed something

[Hawaiis0]

You have looked at or have you tested the wires? Was the supply voltage, earth continuity and coil line continuity all good. There are at least 2 connectors between coil and tacho. Try Jumping a lead to the Tacho from the coil and bypass the earth. Check the crimp on the coil. Mine was found 'on' but loose and not touching.

[fueltheburn]

What stu said.

If in doubt, clean up, re-crimp with fresh terminal and also solder.

Worth noting the voltage stabiliser is next in the circuitry after the tacho.
Are you getting a constant voltage?
It's looking like its DMM time for both continuity and voltage.

[amarshall]

Worth noting the voltage stabiliser is next in the circuitry after the tacho.

Depending on the year - post '85 cars don't have a voltage stabiliser for the instruments.

[Skeggybloke]

Well had the meter out tested wire from coil to rev counter all seems good , while had dash out check the power to counter 12v on green and a good earth , only thing I can think of of is did we put right coil back on as we tryrd a few or has counter died

[amarshall]

Which year is the car ?

My service notes (section MH - 1989 onwards) show White/Black going from coil negative to AB14 and White/Slate from coil neg. to tacho. There's also a white/slate from coil neg. to going to the deceleration relay for the throttle jack and thence to the rev. limiter. All of these components are connected in parallel.

White wires go from AB14 to coil positive and from coil positive to rev. limiter. Also connected in parallel.

The rev. counter itself should earth via the instrument loom to the earthing point on the pedal box, IIRC.

My experience is that the wiring on the spade connectors at the coil, in particular, seem to suffer wear & tear so are definitely worth re-doing.