1977 xj6-c. My tach doesn't want to work. I want to run some tests to check my hookup. I have the white/blue wire on the negative side of the coil running to the round connector on the back of the tack.. I don't know where the spade wire goes, + 12 I believe. I'm running an Allison XR700 ignition system. It seems to work good as the car runs well. Im also runing a ballast resistor.

Can I test the tach by running a wire from battery+ to the spade lug and coil negitive to the round connector?

thanks geneo
brown coupe

 

MMMMMM.

There is something bouncing between the ears on the XR700 and S2 Tacho's, and I will go looking and report back when I find it, dont hold your breath, it may take an hour or 2 or 3.

The Tacho "basically" gets 12V Ign, on one terminal, and the White/Blue spiral wire to the coil -ve is the earth pulse.

 

OK, my notes are all for the V12 cars that ran the tacho from the OEM Opus Ballast Block. When changing to coil sensing, the internal circuitry of the tacho required altering to suit that incoming signal, and I entrusted that to the Instrument Specialists.

You have the same booklet, from what I see, as me. Page #16 may answer your question.

I never fitted the XR700 to any of the 6cyl cars, I opted for the S3 distributor and AB14 Amp, on all of them. Simple to fit, and reliable as hell.

If your spade wire has 12V Ign, that is the same as battery supply, and I would use that. If it does not, then sorting that would be better in my opinion. Jumper wires can sometimes turn nasty in a heartbeat.