Tachometer

[Schnidly]

Dear Forum,

My 1988 90hp Mercury outboard, 0B302485 serial number has a tach problem. I have the simple 9amp charging system which only consists of the ac off of the stator feeding a rectifier, no voltage regulator, and one grey sender wire going up to the tachometer. I removed the rectifier suspecting it to be the problem, but it checked out good, and I checked it with an analog meter twice. I checked the sender wire, grey, to the tach which I removed from the rectifier and any contact with any wires also and it checked out with continuity all the way up to the dash to the backside of the tachometer. When I turn the ignition key to the on or run position the tach zeroes itself back out so I suspect the tach is good? The light inside of the tach housing lights up when the key is on also, not that this has anything to do with the tach not registering. Anyone have any ideas what the issue could be? Oh yeah, I checked the stator, the two yellow leads coming out of the stator and I get a reading resembling a short circuit, then I checked each yellow lead to ground and go NO reading on the wires to ground so I know that is good to go.

Thank you so much for your input

 

[Chris1956]

Re: Tachometer

It sounds like you made all the right checks. The only check (that wasn't clear if you did) is to make sure you have continuity on the grey wire from rectifer to tach connection (disconnect both ends for test), and no continuity to ground on grey wire (both sides disconnected).

Dumb question: You are connecting the grey wire to one of the yellow stator wires, right?

 

[Schnidly]

Re: Tachometer

Thanks Chris, what I did was to disconnect the tach sender grey wire from the rectifier and from the tach harness by the remote control and check it to that point first and I got coninuity from my ground wire and the grey wire with a ground wire jumpered to the grey wire to ground. I then checked from the rectifier(grey send wire grounded to the back of the tach and I got continuity which I expected to have with the grey tach wire grounded. Seems to me everything checked out fine, but maybe tach is just bad???? Like I said, it will zero when I turn the ignition key to run.