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Could someone explain (in simple English) why my stb rev counter works only when it pleases?
Suddenly, it stopped working but occasionally it comes back to life and after a while it goes back to sleep again. I looked at the little plug that attaches to the alternator, it seems a tight fit, sometimes as you move it the rev counter works; then it stops again. I don't seem to be able to secure a permanent contact between the male and female, unless the problem lies elsewhere and it is just a coincidence that playing with the plug makes the counter work temporarily. I have Yanmars 240 4LHA STP's.
Thanks.

The wire could be broken inside the insulation right at the connector. When you move it, it will make contact for a short time and then lose contact. LB

Thank you Les. It seems the malfunction is at the main connector - there are two of them - or at the meter itself. Which means I'll have to live with it till I get back...

Yannis,
Do you have Yanmar tachometers?
If so, they are not driven from the alternator. If some other brand they could be driven from the alternator, but that would be unusual.
My Yanmars tachs are driven from a sending unit that counts the teeth on the flywheel and is mounted on the bell housing.
Is not unusual for the spade (slip on) connector to need to be cleaned. A little corrosion can make the tach inoperative or sporadic.
Most applications I have seen do not use the tach drive on the alternator. I have the alt. drive hooked up to an old set of digital tach just because they were left over from the gas motors.
So, do you have two sets of tachs?


Bill

Bill, thank you.
I'm having a hard time connecting to the internet from where I am...
Yes, I have Yanmar tachs and, yes, I was also told what you're suggesting.Only I cannot spot the connector you're talking about (I'm not a mechanic myself and am in a small island with some mechanics who I wouldn't want to lay their hands on the motors - if you know what I mean - for fear that instead of fixing something they might do the opposite !!).
Where is this bell housing and what does this connector look like? The internet is so slow - when there is internet, that is - that sending pics either way is like having to go to China on a donkey...

Thanks.

The bell housing is where the transmission attaches to the motor. It swells out to accommodate the flywheel, hence the name.

A couple of years ago I had one of my tachs start acting up. I suspected a bad connection at the sender, and as you have experienced, it was hard to find.
Next time I am at my boat I will find the sender again and try to post a description of where exactly it is and how to find it.
Bill

Thank you guys, i appreciate your help.

The only thing connected to the bell i can find are two red cables that are screwed side by side on a thing that looks like a spark plug shaped item. Could that be the connectors and the sender?

Bingo ! It's squeezed right under the oil filling cap, on the rim of the bell housing.
Thanks.