Hitachi alternator query

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CLP

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Can anyone advise how many poles my Hitachi LR155-20 alternator has? Its fitted to a Yanmar 2GM20 and I wish to add a tachometer. The tacho has different settings for different numbers of poles and pulley ratios.

Many thanks in anticipation.
 
Has your alternator got "W" terminal to drive a tacho. They don't normally. Otherwise, I don't know if your tacho will read off the main output, but someone else may know. I've got an idea it's 4 pole, but if you try it, and it works, tickover should be around 800rpm, then you've got it right.
The GM engines normally drive their tachos from the starter ring gear teeth via a pick-up on the bell housing.
 
Hi earlybird, my alternator has a "W" lead fitted. The tacho instructions quote 8,10,12,14 or 16 poles, each with different ranges of pulley ratios. I need to know which number of poles is correct. I've looked at the manual for the alternator but it doesn't say anything.
 
CLP said:
Hi earlybird, my alternator has a "W" lead fitted.
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Then it's different from the LR155-20 described in the Yanmar workshop manual. I'd better withdraw my suggestion of 4 poles. ( I really did once count, but so long ago I've forgotten and the diagram in the manual is not clear enough). However, unless someone does post the figure, I'd suggest the lowest setting, 8 poles, the pulley sizes you can measure, and check against tickover, unless, better still you can borrow a h/held tacho.
 
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