Electric tachometer connections--No Healey content

[Michael Oritt]

I am installing a Racetech electric tach in one of my cars and have a question regarding connections.

The car is 12V negative ground with a conventional coil, a Lucas distributor and a Pertronix Ignitor II system.

After connecting the + and - wires i must choose between a white/black wire which "connects to the switched side of the ignition coil of a contact breaker ignition system" or a red/blue wire which "connects to ECU or electronic ignition tacho signal".

While a Pertronix system is often called an "electronic ignition" my instincts tell me that I should be using the white/black wire. Isn't the Pertronix simply a breakerless system that still grounds the coil in much the same way as do points? It is certainly not an ECU and there is no tach signal output wire to make a connection to!

All input will be appreciated

 

[Keoke]

While a Pertronix system is often called an "electronic ignition" my instincts tell me that I should be using the white/black wire. Isn't the Pertronix simply a breakerless system that still grounds the coil in much the same way as do points?

Regarding this point your assumptions are correct.

 

[John Turney]

I agree with Keoke.

 

[CaptRandy]

Same way when I installed an XJ 6 tach in my AH

 

[Bob_Spidell]

Isn't the Pertronix simply a breakerless system that still grounds the coil in much the same way as do points? It is certainly not an ECU and there is no tach signal output wire to make a connection to!...

True for negative ground Pertronix setups; for positive ground the coil is permanently grounded (unless you use the lead to the anti-theft switch in the boot, as I do). Note the difference in the installation manuals for pos/neg Ignitors:

https://www.pertronix.com/support/manuals/

 

[Michael Oritt]

Thank you all for your responses and I will proceed with the installation.

My initial concern was that choosing the wrong wire might burn out the tach but the more I thought about the less sense that made. On further investigation as to why some electrical tachs, including the Racetech, have different input wires for breaker point sets versus electronic ignition systems or ECU's I found that it simply has to do with the quality of the signal produced and the different inputs have different noise and interference filters, etc. Apparently point sets are "cleaner".

 

[John Turney]

... Apparently point sets are "cleaner".

Some electronic ignitions have multiple spark discharges (MSD) which could definitely mess with a tach.

 

[Patrick67BJ8]

Some electronic ignitions have multiple spark discharges (MSD) which could definitely mess with a tach.

I had my tach rebuilt by Nisonger and I was told it would now work with the high energy ignition systems.