Alternator Tachometer Connection
engines the tachometer signal can be generated by (one of) several different means, including:
1) the alternator
2) the magnetic (Hall) sensor, which counts gear
3) a tachometer signal generator
that is spun by a mechanical take-off
Alternator Tachometers operate off the “AC Tap”* connection on the engine
alternator. As the engine speed increases and decreases it varies the AC output reading to the tachometer. These units offer a stable reading, are reliable and virtually maintenance
free. It is however important to ensure correct alternator belt tension is maintained. Belt slippage will result in a low and/or erratic reading. Tachometers require calibration when first installed, normally performed with a hand held tachometer, reading from the crankshaft.
The AC Tap(s) could be marked
: AC, AUX, S, R, TACH, STA, W, X, N, or P.
Some alternators have more than one tachometer tap.