tach acting weird

[1216bandit]

The engine is a 1984 3 litre mercruiser 130 with electronic ignition conversion. Tach has worked just fine till the last time out. It wont indicated any higher than about 1300 rpm and does return to idle rpm but stays there when the engine is shut off. If I turn the ignition on it will drop down to zero, turn the ignition off and and it climbs a bit. I just cleaned all the connections at the tach but nothing changed. I would like to check the signal source at the engine but with the electronic ignition I'm not sure where its taken from. Any tips greatley appreciated! Thanx....Dan

 

[JoLin]

Re: tach acting weird

An easy trick and it usually fixes the problem.

Pull the tach out from the dash and turn it around )you shouldn't need to disconnect anything). You'll see a small 'pole selector' switch. It's round, has a head that accepts a small screwdriver, and it points to one of a series of numbers stamped on the back of the tach.

Note which number it's pointing to, then with a screwdriver turn the switch back and forth a few times, ending at the original position. Even a tiny bit of corrosion in the switch will make the tach act erratically. 'Exercising' the switch breaks the corrosion.

Also make sure all the other comnnections are clean and tight.

Report back and let us know if it worked

 

[Augoose]

Re: tach acting weird

An easy trick and it usually fixes the problem.

Pull the tach out from the dash and turn it around )you shouldn't need to disconnect anything). You'll see a small 'pole selector' switch. It's round, has a head that accepts a small screwdriver, and it points to one of a series of numbers stamped on the back of the tach.

Note which number it's pointing to, then with a screwdriver turn the switch back and forth a few times, ending at the original position. Even a tiny bit of corrosion in the switch will make the tach act erratically. 'Exercising' the switch breaks the corrosion.

Also make sure all the other comnnections are clean and tight.

Report back and let us know if it worked

I have been living with my tach acting up and jumping around for 2 months now - just came across this post yesterday and tried it - fixed my problem!!!!

You are the man!!!!
Thanks!