tach question

IIBAD4U · 08-17-1999, 07:21 PM

How do tachs work. Do they have a positive wire that when it get's grounded that triggers it? The stock tach on my car (77 mustang II) doesn't work with my ignition. I don't think I have been hooking it up right. Well, I just need to know how a tach works in order to figure it out.

Thanks

351w67MustangGuy · 08-18-1999, 01:06 AM

I just installed a Autometer tach in my 67 and it has 4 wires. Black, Green, White, & Red. White is for the light (just remember white light). Black is ground, Red is hot/positive, and Green goes to the coil. I hope this helps, probably won't though.

brooksgnm · 08-22-1999, 08:21 AM

Tachs work by reading the amount of pulses coming out of the negative side of the coil. Hook it up as follows: White wire to fuse that dash lights are powered by, black wire to ground, red wire to a constant hot(+)wire, and green wire to negative side of coil. If it does not work properly then see if your ignition has a tach output wire on it and hook the green wire up to that. Hope this helps!

08-17-1999, 07:21 PM	#1
IIBAD4U Registered Member Join Date: Jan 1999 Location: Bismarck ND USA Posts: 8	tach question How do tachs work. Do they have a positive wire that when it get's grounded that triggers it? The stock tach on my car (77 mustang II) doesn't work with my ignition. I don't think I have been hooking it up right. Well, I just need to know how a tach works in order to figure it out. Thanks

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08-18-1999, 01:06 AM	#2
351w67MustangGuy Registered Member Join Date: Jul 1999 Location: Bay Area, California Posts: 103	I just installed a Autometer tach in my 67 and it has 4 wires. Black, Green, White, & Red. White is for the light (just remember white light). Black is ground, Red is hot/positive, and Green goes to the coil. I hope this helps, probably won't though.

08-22-1999, 08:21 AM	#3
brooksgnm Registered Member Join Date: May 1999 Location: Union, Ohio, USA Posts: 582	Tachs work by reading the amount of pulses coming out of the negative side of the coil. Hook it up as follows: White wire to fuse that dash lights are powered by, black wire to ground, red wire to a constant hot(+)wire, and green wire to negative side of coil. If it does not work properly then see if your ignition has a tach output wire on it and hook the green wire up to that. Hope this helps!