Tach Repair

[maxfax]

It's official, my tach is whacked..  I have the MK1 gasser tach triggered off a magnetic pickup on the crank pulley..  I did some testing today an the aftermarket tack worked fine..  I removed the factory tach from the cluster and hooked it direct elminating any issues with the car and it's still whacked..   When I first installed it it would jump around from time to time, and got progressively worse.. Now at a tad south of 3 grand it starts to twitch, by 3K and over it drops down somewhere between 0 and 1k and hangs there till the rpms drop below 3k..   

My electronics knowledge is limited but upon visual inspection all the soldering seems tight and the needle is free..  Anyone ever fix one? know where to get one fixed?  OR should I start watching fleabay again?

[rallydiesel]

That would be great if they were repairable. I have a wonky tach too. It's useless above 1500 rpm. Used to work great until the w terminal grounded against the alternator housing. They seem to be getting more  and more scarce and paying over $100 for another cluster doesn't interest me.

There must be some electrical geeks out there. 

[maxfax]

If I were a betting man I would guess that it's the electro mechanical doo dad that physically moves the needle going bad..  Parts are probably kinda scarce for these, but I wonder if even that part from a newer VDO tach may work..  There's a fellow near Lancaster PA that repairs electronic speedometers..  I spoke with him a bit and he may be willing to tackle it if I'm in no hurry..  The biggest issue he has is that he would have no way to operate it..  I think I have enough electronic ability to build something to accomplish this..  It may not be perfectly calibrated, but 100 RPM +/- is probably as close as it ever was...