Optional Rev Counter Wiring - 1970 Series 1 V8

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Fraserp6

Member
I'm looking to fit my recently acquired Rev Counter to my 1970 V8. I ask, before I take all the dash apart, is there any existing wiring for this tacho present on the car, say behind the strip speedo or does the wiring need to be made up?

If the wiring needs to be made up, does anyone know what needs wired to where?

I believe that the spade connector on the back of the Smiths Tacho is the 12v supply from the ignition, then there are two bullet connectors, male and female. I assume one goes to the coil at the positive? Is this the male or female? And where does the remaining bullet connecter wire to?

thanks in advance,

Fraser
 
You'll have to make the harness up. The two bullet connectors are for the sense loop. The sense loop runs from the coil to the distributor, replacing the normal low tension wire from the coil to the distributor. The spade is +12 V.

Yours
Vern
 
On top of what Vern says, it is worth looking at the wiring loom behind the clock. If you can find a line that is joined with male - female bullet connectors then perhaps these are the connectors that you are looking for.
 
Also check if you have a ballast resistor resistor for your ignition coil. If your car has a ballast resistor, you should not bypass this ballast resistor with your tacho wiring.

Peter
 
Thanks for the inpu.

In short, I'd wire the positive of the coil into the back of the rev counter, then take the negative, via the distributor back through the rev counter also?

Is the female fitment on the rev counter for the positive (male) bullet connector?

Also, on a series 1 V8, is there a preferred pick-up point for the 12volts to the rev counter?
 
Fraserp6 said:
In short, I'd wire the positive the coil into the back of the rev counter, then take the negative, via the distributor back through the rev counter also?
Is the female fitment on the rev counter for the positive (male) bullet connector?
Click to expand...

NO! Now there is a wire that goes straight for the distributor to the negative of the coil. You should make this wire pass through the rev counter.
So instead of having one wire that goes straight from the distributor to the negative of the coil, you have to replace it with 2 wires. One will go from the distributor to the one (it doesn't matter what) bullet connector to the back of the rev counter, and the other will go from the other bullet connector at the back of the rev counter to the coil negative.
I hope it's a little more clear now.
 
That makes perfect sense Demitris, thank you. I'll be able to wire that no problem.

Finally though, any suggestion on where to take the 12v supply from? I'm ideally looking to keep the wiring as untampered as possible.
 
Fraserp6 said:
That makes perfect sense Demitris, thank you. I'll be able to wire that no problem.

Finally though, any suggestion on where to take the 12v supply from? I'm ideally looking to keep the wiring as untampered as possible.
Click to expand...

Your first thing to do is to seach behind the dash for the original wiring loom. Just in case the wiring is already there, as it is on the 4cyl cars.
 
The harness for the tach is not there on series 1 4 pot cars unless the car was fitted originally with a tach. However, things were changing by 1970 so there is a chance I suppose. The pickup point for the 12V is from the positive side of the voltage regulator on the back of the speedometer.

Yours
Vern
 
Done. Wired in and the vehicle still runs. Alas, no reading from the Rev Counter, however, that will likely be down to the Simon BBC electronic ignition I have fitted.

Next stage will be to re-remove the tacho and get it converted.
 
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