trying to disconnect my tach

[Boulder Bob]

the wiring diagram I have shows it connects to the "intermediate unit". My car doesn't seem to have one of these - is this possible? I remember my '69 E had one but I can't seem to locate one of these small silver cans in the likely place.

Is there another way to disconnect the tach in the engine compartment?

thanks.

[mike curnow]

pull the black and purple wire from the distributor, depending on the model

[304065]

The intermediate unit is a small silver can that says "einbau senkrecht klemmen unten" on the side. It was used from the introduction of the BHKZ system until October, 1970. So it would not appear on your 73.

The tach wire is a black/purple that starts at the distributor, goes to the electrical console, connects to the speed switch and then runs up to the tach in the dash.

[Boulder Bob]

thanks for the responses - the black/purple wire did the trick. A local Porsche mechanic had mentioned that he has known of a defective tach causing a misfire.

I still have not found the misfire that is in synch with the tach bouncing (minor movement, but definitely not steady) - had the dizzy out, points looked OK (had them out), re soldered the wire that connects the top and bottom plate (not pretty but I have a zero ohms reading), dwell is within spec. It does this with the RPM transducer in or out of the circuit.

I have access to an Oscilloscope and I'm wondering if that will help find the problem - or maybe take the dizzy back out and put it on something like a Sun distributor tester (or an actual Sun Distributor tester ), just to eliminate the dizzy as the problem.

At this point my other idea is to swap out the CD box with a known good one.

Could I have a ground issue?

[304065]

bouncy tach= bad vr
what is system voltage?

[Boulder Bob]

bouncy tach= bad vr
what is system voltage?

I've checked in the past but will check again and report back

thanks