Another tach problem

[scalebuilder]

I have a 1995, 75 HP Mariner. The tachometer doesn't work when the motor is running. However, if you turn the key on without cranking up, the tach will slowly creep up. Once the engine cranks, the needle pegs to zero and won't budge. Am I looking at replacing the tach or something more serious?

 

[RushFan]

Re: Another tach problem

Make sure the connection behind the dash on the tach are tight and not corroded. It may have push-on connectors too. Again, be sure the connectors are free of corrosion and are making a good contact.

This sounds like a classic case and the tach is faulty. If you tap the tach face and the needle is erratic, bad tach.

 

[scalebuilder]

Re: Another tach problem

Thanks Rushfan. I checked and cleaned the connections last night. No luck. Even if you tap the tach it won't move.

 

[recess]

Re: Another tach problem

Tach problems can also be associated with a bad rectifier (the thing that converts ac current to dc). If you have a voltmeter, check the output from the dc side ( + and - ) and see if you are putting out dc current. You could also meter your battery. Before you start the motor, check your voltage. After you start it up, the voltage should begin to rise. If it doesn't; bad rectifier. If it does rise, then sounds like your tach.

 

[scalebuilder]

Re: Another tach problem

Thanks. I'll check it this evening.

 

[RushFan]

Re: Another tach problem

Tach problems can also be associated with a bad rectifier (the thing that converts ac current to dc). If you have a voltmeter, check the output from the dc side ( + and - ) and see if you are putting out dc current. You could also meter your battery. Before you start the motor, check your voltage. After you start it up, the voltage should begin to rise. If it doesn't; bad rectifier. If it does rise, then sounds like your tach.

That was my next post for troubleshooting... Good post recess!

 

[Barnacle_Bill]

Re: Another tach problem

Tach input is AC not DC. Power from the switch is DC.