Them analog tachometers

You are using a Pertronix, are you not? If not, as my fading memory of things like distributors flickers dimly, it seems to me there was something about a failing capacitor causing similar problems. -BaH

I did once have a bad condenser that caused engine problems and associated tach issues, but I am now running pointless and the tach has just now started acting up with no associated engine problem. It's a tach issue and I'm wondering if anyone know what happens when you yank the +12 wire from a tach. Does it drop to zero, or maybe sit at some midrange position?

"Mike Rocket J. Squirrel Elliott" >

my Sun "supertach" drops dead when you disconnect the power supply...

Interesting . . . anyone know the theory of operation of analog tachometers?

....sure do. You hook up all the wires..and "theoretically" the tach works...

...glad I could beof assistance. =-)

...Gareth

I'll remember to call on you the next time I need some real brainpower.

If you have a timing gun with a tachometer on it, you could disconect the tachometer on the dashboard and hook up the timing gun. If it reports rpm correctly, then the problem is in the tachometer, otherwise check the wiring.

If you have a soldering iron and have some experience on soldering PCBs, then you might want to dismantle the tachometer and look for connections that might have come loose from vibrations and need re-soldering, or for some electrolytic capacitor (the cylindrical ones with polarity) that might have leaked and replace it with a new one. Look also for cracks on the PCB or any other obvious problems. Other than that, there isn't much you can do to fix it.

Bill, '67 Bug.

Hi Bill,

The engine is fine -- I guarantee that it has not been running at a steady 2,000 rpm with no variation for the past two days. I been driving the bus and I would have noticed, I think. I agree with you that the problem might be in the tach, but my posted question was just to find out what something like a working round face VDO tachs might do when the

Yah I been too lazy to get under the dash to look, and it sometimes fixes itself. I wuz just wondering if anyone knew.