Sometimes my tack is stable, sometimes it fluctuates wildly.

Points?
Tach?

Any ideas?

Will

My 74 had this problem. I never figured it out, but I've heard that it's possibly a ground problem.

On my /6 the wild, floaty tach was accompanied by an engine miss. Oddly enough, the engine and the tach would settle down while the brake pedal was pressed.

The problem was a bad cd ignition module. Pressing the brake (at idle) turned on the tail lights and the voltage drop would settle the module which settled the tach. Replacing the module cured the miss and the weird tach.

Carl

one word ...

relayboard

i had the same thing, never figured it out.
until i bought a (brand new) relay board and voila!™ problem solved ...

i think after 30+ years the soldering starts to crack ...
Andy

My tach acted crazy (stopped, then worked, then stuck, etc.) when I had a bad coil. New coil fixed tach problems.

The tach in my 72 started doing the same thing several days ago as well as my speedo. Speedo seems to bounce until I reach about 30 mph.

Could a bad coil cause both instruments to act this way?

I had a bosch blue coil that wasn't mounted 100% securely and it would vibrate its way until the negative side would occasionally touch the sheet metal and ground out. But that cause the engine to miss, as well as the tach to jump.

Preventative maintenance. Take down the fuse panel and clean the ground point behind there. You'll need a screwdriver and a 10 mm socket wrench to do it. Only takes a second and can clear up some weird stuff.

the speedo is mechanical, you need to lube the speedo cable, the tach wobble is also in my car it floats wildly. and i winder if the thing is really working semi correctly at all..

still love my car.

914 tachs have a lot of odd problems. The "float" problem, where the tach overshoots and undershoots on large rpm changes is due to a non-functioning mechanical damper in the tach (according to discussions I've had with Palo Alto Speedometer). Send it to them or to the shop in SoCal, probably $100+ to fix.

Mine's done this for 20 years, I'm just used to it now and don't care...

Regarding the speedometer:

I disagree... for precisely the same reason. The speedo gauge is mechanical. I don't want lube backing up the cable into the gauge itself. They work 30+ years without being lubed so I'm not about to introduce lubricant into something that is built that well.

If the speedo cable is binding, fix the problem: replace the cable or find the kink or sharp bend.

-Rusty

replace points condenser in dizy and check ground.

Hey
Points and condensor seems to have fixed this.