The Tach on my 1972 Grand Banks 32 stopped working. it appears to be electronic (off alternator I'm told?) anyone have any experience with this.

[Damariscotta]

The Tach on my 1972 Grand Banks 32 stopped working. it appears to be electronic (off alternator I'm told?) anyone have any experience with this.

 

[DavidM]

I had a boat, can’t remember which one, that had an electronic tach as you describe. There was a wire from the alternator that picked up the pulses from the alternator and sent it to the tach. The wire is likely corroded and not making contact at one or both ends.

Find it, disconnect each end and clean it up and give it a little blast of WD40 or similar and reconnect.

David

 

[Grand Illusion]

If it's like my 1968 GB, the early Lehman tachs are driven from a pulse generator located directly below the coolant pipe running down the starboard side of the engine. The pulse generator is driven off of the cam.

Mine also stopped working after I did some work, and I realized the coolant pipe was touching both contacts and shorting the signal. I cut the bulb off of a turkey baster and stuck it over the tach sender to insulate it electrically from the coolant pipe and that solved my issue.

When I consulted with Brian Smith at American Diesel about this, he told me the pulse generators aren't available anymore, and recommended converting to an alternator-driven tach as the modern equivalent. So, if it turns out your sender is actually dead, that might be the path of least resistance.

 

[SteveK]

The pulse generator for OEM tachs is not available. But you can get a new tach(s) to go with a new generator.
That is what I did with 71 GB

 

[jleonard]

The tach runs off the "R" terminal on the alternator.

 

[Damariscotta]

Thanks for the information

 

[jgwinks]

If the alternator is not producing current, an alt driven tach will not work. Are you sure the alternator works? Does it charge the batteries? This is a common problem on boats with big solar panels, the solar keeps the batteries full so the alt doesn't kick in, and the tach doesn't work. It can also happen for the first few minutes after leaving the dock if the boat was plugged in for days. The simple fix is to turn on a fairly large DC load. The alt will come on and the tach will start working. Sometimes just the nav lights are enough load if they're incandescent bulbs and it's perfectly ok to have them on in clear daylight.

 

[Damariscotta]

I will explore this recommendation. Thanks.