Jumpy tachometer

[eb61636]

I just installed a Pertronix on my 050 distributor and the tach is jumping all over the place all of a sudden.

I had this same exact Pertronix unit on my old engine, so I know it works and my tach was working fine 10 minutes before with the points installed.

I tightened all the connectors...checked my air gap (.030"), cleaned and lubed the rotor and cap, ensured the distributor was all the way down in the hole, etc.

This is the third Pertronix unit I have used (not on same car) and the first time I've ever had problems with one.

Any ideas on why my tach swings intermittently on its own since I installed this Pertronix?

Thanks,
erik.

[ron69912t]

Erik:
Before I installed my Pertronix on my 050 I e-mailed their tech dept for installation instructions and I recall the tech said if my tach malfunctioned I should add a certain value resistor to the tack connection at the coil. I don't remember the specifics of the resistor but if you e-mail or call Pertronix they will help you.

Fortunately, I did not have a problem with my tach.

You can find them on the Internet.

Good luck,

Ron D

[craign]

Erik,

Here is the web link

www.pertronix.com

I recall seeing something about a resistor use also on some systems in my instructions.

Prior to installing my pertronix, my tach started doing the same thing. 30+ year old coils do wear out eventually and a new blue coil fixed it right up.

Craig

[eb61636]

You both make a good point about the resistors...I'm going to give Pertronix a call.

The thing is...there was no resistor on the engine that was in the car before and the setup was exactly the same:
New Bosch Blue coil
New stock plug wires
New 050 dist.
New Pertronix
New W6BC plugs

Stranger things have happened though....

Thanks for your responses,
erik.

[ron69912t]

Erik:
I assume you have the right wires hooked up to the coil from the Petronix. I had them reversed and the tach did not work at all.
If I recall corectly it is red wire to + (ignition switch side) and black wire to - (negative) posts on the coil.

Good luck & let us know what they tell you.

Ron D

[craign]

Ron,

I was told if you cross the wires at the coil you just toasted your Pertronix, I take it you did not suffer this?

I also recall in the instructions they recommended a resitance range for your coil to determine if you needed a resistor or not. Bosche blue fell right in to their spec and didn't require a resistor.

Craig

[eb61636]

Craig,

I know if you cross the wires you weld the points pretty quickly, don't ask me how I know.
So with that in mind and the fact that the car runs beautifully...I don't think I crossed the wires, but the htought did "cross" my mind.

I'm going to call Pertronix.

If and when I fix this, I'll report back.

thanks for all the responses/suggestions,
erik.

[ron69912t]

Craig:
Yes they say if you cross the Pertronix wires it's toast. But in my case I actually drove the car around to see if there was any improvement and noticed the tach was not working as I parked it. The next day I discovered the wire mix up, switched them around and everything worked and still does. Maybe I was just lucky.

Ron

[eb61636]

Pertronix has no clues other than to ground the breaker plate which I already tried to no avail.
I put my points and condensor back in and no more jumpy tach...I'll be calling Pertronix again for another unit.

Don't get me wrong...I love these Pertronix units, I have them in all my collector cars and they usually work great...I'm thinking this is an isolated problem.

thanks again for all the advice,
erik.

[cgarr]

Erik, I had this problem and it was a loose wire, it was jumping all over the place, a bad connection, I would guess could cause it also. When you order another unit ask them if they have units that fit the 031 dizzy.

Thanks

Craig

[ron69912t]

Craig:
Where did you get your OEM Blue Bosch coil?? I probably need one too.

Thanks,
Ron D

[craign]

Ron,

Not sure which Craig you were referring to, I got my blue coil at the local VW shop.......much cheaper than what I am seeing on Ebay.

Try www.cbperformance.com or any of the 912 Rendezvous sponsors. I think I paid about $12-13 for mine but I know it was no more than $15.

Craign

[eb61636]

Actually, www.cbperformance.com has them for $27.95, but that's still a good price...it's the best coil I have ever used.

You could try www.busdepot.com as well, they are good.

erik.

[ron69912t]

Craig:
You were the one I was asking..thanks.

CB says the Bosch Super Blue Coil is a larger capacity coil (than the standard?).

My Delta Mark Ten-B CD ignition system says NOT to use high intensity coils with it.

Is the BSB Coil the stock coil on our 69 912's?

Mine looks like the BSBC it has the same shape & color decals but you cant read them.

Thanks,
Ron D

[craign]

Ron,

I don't beleive the "super" blue is stock, I still have my stock coil in the garage, I'll have to see what I can make out on it. The case is brown if that is any indicator, unless that is 30+ years of garbage on there.

Not sure if there is a difference with between a "super" blue or regular old blue coil or if we are just mixing semantics.

anyone?? Is there a difference between the Bosche Blue and "Super blue" coils???

Craign

[eb61636]

They are the same coil.

The brown one is actually black...black Bosch coils were stock on 912s.

erik.

[craign]

Erik,

Thanks, I guess I know what heat will do to a black coil over time......

That also answers why I have seen blue coils painted black on concours 912's.

Craign

[ron69912t]

Here is a possible fix for jumpy tachs with a Pertronix set up. I got it from one of the Pertronix dealers tech service.

Thanks,
Ron D

[eb61636]

It's funny you just posted this...I just bought the diode rectifiers last night at Radio Shack.
Now to wire them in????

erik.