Thread: RPM pickup off alternator

The alternator may appear to be charging fine but a poor signal from the tacho usually indicates the regulator /brushes on the way out. Depending on the model, it might be a fairly straightforward DIY job requiring a couple of spanners and a phillips head screwdriver... and 30 mins of your time to replace same.

good luck!

Your answer is to get a Bosch alternator!

I hate working on the Lucas/Mareli rubbish alternators. Such a stupid design compared to the Bosch modular units. HOWEVER, if you're getting erratic signal for the tacho and you are feeling brave, the signal wire comes straight one of the field windings.

I've re-engineered a Bosch unit to fit.

The tacho connection is at one of the most reliable, robust parts of the alternator, namely at one of the three connection points of the stator. No diodes are needed to process the signal. So long as all the parts of the alternator are functioning as normal you should get a tacho output. Absolutely any alternator can be opened up and a wire soldered to one of these three points. I once tried a Falcon EL alternator I had lying around, I thought it shouldn't be too hard to adapt it to a serpentine engine. The pulley will need to be swapped from one alternator to the other.




This one had a vee belt pulley for an early RRC conversion I tried.

When our alternator was reconditioned earlier this year the reconditioner sent it back without the fitting for the tacho readout. Our workshop sent it back and insisted they fit the tacho connection, which they did. Now it works fine. So, it must be possible.

So ...... I should be able to get a Bosch alternator of appropriate amperage and fit an rpm pick-up wire to one of the stator connection points and all will be well?

Any particular model or part # for a Bosch unit I should be looking for?

Seeing as one side of the EL alternator lines up 100% you will need to steady the other side with some kind of bracket, try this part number:

NEW Bosch Ford Falcon 6 Cylinder EF EL 108Amp Alternator BXF1260A Genuine CAR PR | eBay

I would try one myself but there's no serpy engine handy for me to fit it to.

If you get a Bosch alternator and need a hand soldering in the W terminal for the tacho, sing out and I would be happy to do it for you - I've done a few before.

Cheers - Gav