Erratic Tach - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cleatussnow · 07-13-2003, 06:19 PM

I purchaced a tach dash for my truck and it is working intermittantly. 75 percent of the time when I am driving it does not work. However there are times when it is all over the scale... from 500 to 3500 and back. Then there are times, about 5 percent, when it works just fine...

I was thinking it was a ground. Is there a place to ground the tach? I have it hooked up now with the left wire to ign unfusd. and the other to my HEI. Is there supposed to be a ground on the nut in the center?

Any help is appreciated.

Alex Hayley · 07-13-2003, 07:34 PM

Try running a wire from the dash housing to a good ground area in your cab. See if that makes a difference. I know my tach did not work at all until it was well grounded.

cleatussnow · 07-14-2003, 07:47 AM

I'll try that... It is the same thing that my old man told me...

(TTT)

Huck · 07-14-2003, 08:39 AM

The instrument cluster printed circuit has a very common problem of spliting the ground on one of the corners where the harness plugs in. When this happens, you can loose your ground to everyting on the circuit including the tach which uses the cluster housing for it's ground. If everything else is working OK, go for a direct ground wire from the metal portion of the housing to your dash.

07-13-2003, 06:19 PM	#1
cleatussnow Registered User Join Date: Jun 2002 Location: Pleasanton, CA Posts: 162	Erratic Tach I purchaced a tach dash for my truck and it is working intermittantly. 75 percent of the time when I am driving it does not work. However there are times when it is all over the scale... from 500 to 3500 and back. Then there are times, about 5 percent, when it works just fine... I was thinking it was a ground. Is there a place to ground the tach? I have it hooked up now with the left wire to ign unfusd. and the other to my HEI. Is there supposed to be a ground on the nut in the center? Any help is appreciated. __________________ "What we are dealin' with here is a complete lack of respect for the law...." Beuford T. Justice

07-14-2003, 07:47 AM	#3
cleatussnow Registered User Join Date: Jun 2002 Location: Pleasanton, CA Posts: 162	I'll try that... It is the same thing that my old man told me... (TTT) __________________ "What we are dealin' with here is a complete lack of respect for the law...." Beuford T. Justice

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07-13-2003, 07:34 PM	#2
Alex Hayley Registered User Join Date: Jul 2000 Location: NC Posts: 987	Try running a wire from the dash housing to a good ground area in your cab. See if that makes a difference. I know my tach did not work at all until it was well grounded.

07-14-2003, 08:39 AM	#4
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,269	The instrument cluster printed circuit has a very common problem of spliting the ground on one of the corners where the harness plugs in. When this happens, you can loose your ground to everyting on the circuit including the tach which uses the cluster housing for it's ground. If everything else is working OK, go for a direct ground wire from the metal portion of the housing to your dash.



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