1983 85HP: Tach finally added, but doesn't seem to work?

[Benz Mondi]

OK, I added a 20-pole Tach two years ago, but am only now getting around to hooking it up. I've located the purple wires on the dash and at the motor ends. I've tested the continuity from the dash to the strip connector at the motor and from the strip connector to the OEM rectifier. All are good. Hooked up the purple wire to the gauge and all the other wires to the gauge. Fired up the motor, Tach still at zero. While the motor is idling, I hooked up a volt meter to the purple wire at the strip and got a reading of 6.34 same at the rectifier. Increased the idle speed, no change in voltage value. Is my tach dead or what?

 

[pnwboat]

Re: 1983 85HP: Tach finally added, but doesn't seem to work?

There are two stator wires that go to the rectifier. The tach is connected to one of them. If one doesn't work, try the other one.

 

[Jiggz]

Re: 1983 85HP: Tach finally added, but doesn't seem to work?

As mentioned, the purple wire for the tach needs to be connected to one of the yellow wires from the stator that connects to the rectifier. And the battery wire that connects the tach to the battery should be connected to the auxiliary terminal of the ignition switch to prevent draining the battery when the engine is not running.

 

[jerryjerry05]

Re: 1983 85HP: Tach finally added, but doesn't seem to work?

I thought the tach lead was grey?
The purple lead is the power lead on my motors.(I think)
Will get out and look.

 

[Benz Mondi]

Re: 1983 85HP: Tach finally added, but doesn't seem to work?

I thought the tach lead was grey?
The purple lead is the power lead on my motors.(I think)
Will get out and look.

The sticker on my motor says the tach wire is the purple one. I don't have a grey wire listed.

 

[Benz Mondi]

Re: 1983 85HP: Tach finally added, but doesn't seem to work?

There are two stator wires that go to the rectifier. The tach is connected to one of them. If one doesn't work, try the other one.

OK here's pics of my set-up. I'm assuming that this black box is the rectifier and other than the black and red wires (ground and battery according to the label on the motor), the two yellow wires you refer to are for mine green with a yellow stripe. The purple tach wire is connected to the bottom green/yellow and so I should move it to the other green/yellow above it?

 

[jerryjerry05]

Re: 1983 85HP: Tach finally added, but doesn't seem to work?

The purple wire is the tach,Sorry

 

[Jiggz]

Re: 1983 85HP: Tach finally added, but doesn't seem to work?

Your connections seems to be correct. You are right, the green/yel wires are the input to the rectifier from the stator. So all you need to make sure now is to verify the tach is properly powered (12V battery power and ground), properly set for a 20 pole operation and the signal wire (purple) connected. And the tach should work. Otherwise, it could be the tach is faulty. But before jumping to that conclusion you can dismount the tach from the dash, take it over to closer to the motor and connect it directly to the battery using small jumper wires (alligator clip) and then connecting another signal wire directly to the purple wire on the rectifier or any of the two green/yel wires. And if the tach works, then you have a wiring problem. If it doesn't work, then it is faulty!

 

[Benz Mondi]

Re: 1983 85HP: Tach finally added, but doesn't seem to work?

Your connections seems to be correct. You are right, the green/yel wires are the input to the rectifier from the stator. So all you need to make sure now is to verify the tach is properly powered (12V battery power and ground), properly set for a 20 pole operation and the signal wire (purple) connected. And the tach should work. Otherwise, it could be the tach is faulty. But before jumping to that conclusion you can dismount the tach from the dash, take it over to closer to the motor and connect it directly to the battery using small jumper wires (alligator clip) and then connecting another signal wire directly to the purple wire on the rectifier or any of the two green/yel wires. And if the tach works, then you have a wiring problem. If it doesn't work, then it is faulty!

The tach was faulty. The stud at the back of the tach for the signal is loose and has intermittent contact. I tried pulling it up and then tightening the nut so it didn't move with only limited results so I replaced it with another 20 pole tach and all is well at about 1000 rpm's and steady when already warm. Thanx.

 

[Jiggz]

Re: 1983 85HP: Tach finally added, but doesn't seem to work?

Good on you and enjoy! Men, you sure are becoming a better technician on each post!