Tachometer

[Guest]

I am installing a new engine panel. No problem with anything regarding sensors, wire looms etc. (all supplied) However, I am left with the tachometer wire to attach to the alternator. The old tachometer ran off an engine sensor. Can any one tell me where it goes on to a Lucas alternator. There is a spare spade connector by another one with a wire attached inside the alternator casing but I am hesitant to try it in case I blow something up !!!

 

[Guest]

It is the one marked "W", if you dont have it, app 1988 ford petrol cars have it, get one from a breaker, replace the bearings/brushes, instant 60 amp alternator for £20. Rick

 

[Guest]

You may have a problem - If your 'old' tachometer used an engine sensor, it may not be compatable with one that was designed for alternator drive. Engine tacho sensors basically work by 'counting' the ring gear teeth on the flywheel - each tooth passing the sensor produces a small pulse in the sensing coil. The calibration of the tacho head would be for a specific number of ring gear teeth. Alternator tacho ouput is alternating current, the frequency of which is proportional to the speed of the ALTERNATOR, so reduction for drive pulleys must be taken into account in order to get an accurate reading. I have never tried running a tooth counter tacho from an alternator so cannot make any suggestions - sorry.

 

[Guest]

AS your tacho is designed to connect to an alternator, all you need to do is to remove the alternator cover to gain access to the stator windings where they are soldered onto the rectifier/diode assembly. Simply solder a thin (0.5sq mm) cable to one of the 3 windings & lead it out through the cover. This will output the Ac signal required by the tacho. It works.

 

[Guest]

As your tacho is designed to work from an alternators AC output, if your alternator doesn't have one, simply follow these instructions to add one. 1) Romove alternator cover to expose the rectifier stack. 2) identify the 3 thick copper wires which connect the stator windings - they will 'disappear' down into the interior of the alternator. 3) Solder a thin wire (about 0.5sqmm) onto any one of the thick copper wires where they are soldered onto the rectifier. 4)Lead out this new wire through the cover & connect it to your tacho. If often had to do this for local fishing boats, when they've not been able to get hold of alternators with a W terminal. it always works. Regards.