Pertronix / Smiths Tachometer solution?

[CG901]

Recently had a Pertronix distributor installed in my S2, but as others have experienced, the Smiths tachometer no longer functions. I was told to send the tacho to Nosingers and install new internals compatible with 'all electronic ignition systems'. Before I do that, I contacted Pertronix, and they sent me this document. Has anybody tried this and been successful?
Thanks - Scott

[robertverhey]

Did fitting the pertronix co-incide with a change to negative earth? If so this seems like a good, fairly cheap option

http://www.ebay.com.au/itm/380578001095 ... 1423.l2649

[CG901]

The PO had converted to negative ground, but hadn't mentioned any problems with the tachometer. This unit looks worth trying. Thanks.

[AHM]

I don't know anything about Petronix.

But a good cure for Smiths Tachometer problems is to ensure that the coil is fed from the rev counter only. The electronic ignition should be fed from a different lead ie an additional lead from the ignition switch.

[collins_dan]

I have Petronix ignition and smith's original tach. I powered the Petronix via a separate line from the fuse box and everything works fine. Dan

[CG901]

Dan, which Smiths tach (what year), and are you running negative ground?

[collins_dan]

1970 S4 with negative ground.

[stugilmour]

Scott, I got my RVI external loop tach to work with the Pertronix by following the suggestions in the instruction sheet, including adjusting the tach reading. I also powered the Pertronix with a separate lead as suggested above, which is strangely not as per the Pertronix instructions that came with the unit. Had not seen the sheet you provided before.

The bad news is it all worked for about a year and then the tach started going unstable again. Suggestions here in previous threads are that the 50 year old components in the tach need replacement. I sent mine to Nisonger's for conversion and it all works well now.

So the general advice is powering the Pertronix separate from the coil and using one loop will work with a properly working RVI tach. Trouble is, most of the tachs that have not been serviced aren't up to it due to aged components. If not repairing the tach components yourself, might as well get it converted to modern design by the pro's rather than serviced.

The eBay kit looks like a good one. If you try it, maybe take a few pictures and post how you get on? I had the back off my tach in order to drill a hile for the adjuster screw, and I would think installation of the eBay kit wouldn't be too bad. For comparison, IIRC the conversion at Nisonger's was about $350 with shipping.

Another quick note. During the time I was fiddling with the tach adjustment, I realized it was impacted by ambient temperature quite a bit, with the readings changing roughly 300 RPM as the unit warmed up. Don't have this issue since conversion. Just thought to add this when I saw the eBay listing remarking on the thermal stability of the unit.

Best of luck on the repair.

Stu

[pharriso]

Do a search here on Spiyda, I installed one & have had no issues!
They will even install for you if you can't do it yourself

[CG901]

Thanks for all for the helpful suggestions. Will update this post after tacho surgery. Scott

[mark030358]

Just had my S4 tach converted by Speedy Cables. Seems to work (just reving the engine) however when I press the horn it shoots right round the scale "Noise" on the signal wire methinks

I never got old tachs to work properly on two elans and two europas, got them modified instead...

cheers

Mark

[nomad]

I've had similar problem's with the Smith's RVI tach's and just wanted to mention that there is another cheap option . If you scour the salvage yards for a modern vehicle tach with a similar degree of sweep to the needle its often not that hard to swap the guts to your Smiths case.

Kurt