The Ford Barn - View Single Post - Burned-out tachometers

markdtn · 03-26-2026, 08:39 AM

I had a similar problem. I have an 8N tractor with an 8BA. 12V system. I had a 6V coil and ballast resistor. I bought a marine tach with hourmeter. Would not read over 1000 rpm. Thought maybe it was bad. Bought a China one on Amazon, same thing, sent it back. Then I bought a new VDO tach, same thing. So I said maybe it doesn't like a 6V coil so I bought a new 12v Bosch Blue coil and removed the ballast resistor. Same thing, could not get it to go over 1000 RPM no matter what I did. Settings checked and changed multiple times "just to be sure" but most tachs seem come out of the box set up for V8. I finally gave up and bought an alternator with tach drive and an NOS Stewart-Warner mechanical tach. It works great now.

No help for you I understand, but just to say I feel your pain.

03-26-2026, 08:39 AM	#4
markdtn Senior Member Join Date: Jun 2016 Location: Chattanooga, TN Posts: 192	Re: Burned-out tachometers I had a similar problem. I have an 8N tractor with an 8BA. 12V system. I had a 6V coil and ballast resistor. I bought a marine tach with hourmeter. Would not read over 1000 rpm. Thought maybe it was bad. Bought a China one on Amazon, same thing, sent it back. Then I bought a new VDO tach, same thing. So I said maybe it doesn't like a 6V coil so I bought a new 12v Bosch Blue coil and removed the ballast resistor. Same thing, could not get it to go over 1000 RPM no matter what I did. Settings checked and changed multiple times "just to be sure" but most tachs seem come out of the box set up for V8. I finally gave up and bought an alternator with tach drive and an NOS Stewart-Warner mechanical tach. It works great now. No help for you I understand, but just to say I feel your pain.