Pertronix 3 with a SAAS tachometer...

[mungus]

I fitted a suite of new SAAS gauges to my engine test stand. This included their 3.5" tacho. Looks great! I've been running my built 390 FE on it for a while and the Pertronix 3 / flamethrower system works well. Quick starts, runs nicely. Timing is fine. Strong spark. Yippee.

Problem is it makes my test stand's SAAS tacho nuts. Using SAAS spec wiring, it spikes like crazy and goes full scale (9K) and triggers the shift light with barely any throttle.

I web searched Pertronix's site and emailed SAAS in Melbourne. SAAS OZ didn't seem interested that their Tacho had problems working with a popular ignition system. I suggested dropping it in for testing but they weren't interested. After several calls and being handed around the office all I got was suggestions of googling Pertronix, or "maybe a resistor will help"... (wow thanks). In the end I got the best (poor) result with a ceramic coil ballast between the sense wire (green) and the dizzy neg as one Pertronix PDF suggested. That got the (occasionally) steady idle RPM close enough to my timing light's displayed RPM. But it still spikes so much (>1/2 the time) that its useless. I also tried a few different resistor values (10/15/50kO etc) and a capacitor as was also recommended, but none worked as well as the ballast.

Regardless its useless as is, and a waste of $. There is a bunch of hate on the web about the Pertronix 3 regarding tachos etc, but that's no help to me. I do have a series 1 ignitor on the shelf but would prefer to run the 3 for the rev limiter function and the elimination of the ignition left on cooking the ignitor issue. I am considering popping the little OEM coil and the Ignitor 1 on just to see if that solves it. That would indicate to me that SAAS's aftermarket tacho can't handle high energy aftermarket ignition systems, i.e. not fit for purpose.

So are there any electronics / instruments gurus amongst us? Or has anyone had good results out of the box on a P3 equipped classic Mustang with another aftermarket brand? If so I might test mine with the P1 and if its good, cut my losses and put it on eBay. And although it will mean an unmatched set, buy something that actually works...

This also makes me wonder if it will work with my new factory type tacho too! Although the guy who restored my cluster (Ken Marsola, TX) did say it would work with Pertronix no problems...). I've read sad stories about them cooking the factory tachos... I guess Ken may use modern internals in his new Tachos.