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Wed Aug 28, 2013 2:27 am

i'm assuming that there isn't one already available, so, how hard would it be to design/make a "black box" that will take the input signal from the coil like a normal tach and put out the signal needed to run a 5000RPM early beetle tach or an alternator sensing diesel tach?

I know I personally would like a diesel tach signal converter/generator and i'm sure there are many more early 5k tach's than there are senders.

Wed Aug 28, 2013 6:04 am

North Hollywood Speedometer converts these to electric. The cables tend to break on the sending unit. They have to bend up and turn at a pretty sharp angle. I have seen a few 5k tachs, but only a couple senders.

Wed Aug 28, 2013 7:39 am

Henry,

Joe is right. Of the 25 vdo 5000 tachs I know of only 5 that have the original cable. Is there an instrument shop in Australia that can do a conversion for you? Do you have a 5000?

Wed Aug 28, 2013 8:34 pm

I've also been looking for a similar solution. I'm surprised there's no source for this sort of thing

Thu Aug 29, 2013 12:46 am

hi harris I have a 5k but it isn't a original vw 5k, it is a late 60's diesel base with a striped 5k face, we talked about it a while back.

I know you can get them rebuilt with new innards, but to me using the tach as is with a sender/converter is a much more elegant solution.

Thu Aug 29, 2013 7:16 am

The diagram below is from Joe H first answer above. This will give you some idea what your looking for. Note, as Joe mentioned, the tight turn the cable takes from the crank pulley to the electric sender.

Two photos borrowed from the gallery. This is a little different configuration with a longer cable.

Thu Aug 29, 2013 10:16 am

Could probably do it with a prox sensor mounted in the bellhousing reading the flywheel teeth.

Thu Aug 29, 2013 9:19 pm

There's always the Porsche style oil pump mechanical sender

Thu Sep 05, 2013 7:04 pm

How 'bout this puppy?

http://www.thesamba.com/vw/classifieds/detail.php?id=1524111

TACH-ADAPT.....the little black box that makes your tachometer work right! This digital tachometer rate adapter makes your existing tachometer display correctly on any four, six or eight cylinder engine. This adapter goes in line with your current tach signal and changes the voltage. The pulse rate conversion feature makes it possible to match your vintage tach to a four, six or eight cylinder engine. This item is easy to install and can be concealed in the instrument panel or mounted to the engine compartment. This item has a four wire connection and works with points, electronic ignition or CDI systems. The pulse restoration allows the tach to to trigger properly from modified ignition systems. The pulse filtering system cleans up waveforms and cleans up erratic behavior. This item fits all models, including 356 models that have upgraded from a 6V system to a 12V.

Fri Sep 06, 2013 2:22 am

that's almost it. (I think)

Tue Sep 17, 2013 1:59 pm

If you search ebay for long enough you can probably find a modern VDO generator sending unit for diesel tachs, connected to a 2:1 ratio gearbox (diesel tachs are calibrated to a 1:2 ratio). I've seen such a unit before. It was on German ebay. It would be possible to fab something up in the way of a drive cable with a milling machine and lathe. I don't see any commercial value in producing an electronic solution for tachometers that are missing a generator unit, there are not many tachs out there and I doubt anyone would be on board for this particular type of solution.

Thu Sep 19, 2013 2:53 am

Years ago I found a site where someone had modified another 6V electronic tachometer to connect to the coil, to generate a signal to use as input into the 5000 RPM tacho. Of course now I can't find that info, but was going to see if a local speedo shop could do something similar. Replacing the internals with modern electrics would be a last resort, as it's no longer an original vintage tacho.