How to trouble shoot a tach

[solar7647]

I have a new set of Telaflex Artic gauges hooked to my 3.7L with points and it seems that my tach is shorted.
When everything is hooked up I get no spark but if I remove the sending wire from the coil to the tach I get spark thus leading me to the conclusion the tach is shorted.
I am a little lost in trouble shooting to determine if the tach is bad, I can?t find any information on the subject that explains how to trouble shoot the actual tach to determine if it is bad.
I would like to rule out the tach or prove its bad before I start going through the wiring. The wiring harness is just going to be the bigger pain so I would like to start with the tach first that way I don?t go through the harness to latter find out I was sent a bad tach.
I know it is compatible with the engine set up, I made sure of that before purchase.

To sum up the question: how do I trouble shoot the actual tach meter to know if it bad before checking the wiring harness?

Thanks
.

 

[BaileysBoat]

Re: How to trouble shoot a tach

Could it be you have the tach power and signal wires mixed up?

 

[BaileysBoat]

Re: How to trouble shoot a tach

Found this for you

http://www.jamestowndistributors.com/userportal/woeimages/howtos/Large/837h.jpg

 

[solar7647]

Re: How to trouble shoot a tach

I have that scymatic and that is how i have it hooked up. I know I dont have the power and signal wire mixed up. the signal wire is gray and the power waire is purple and comes of the ignition.

I need to know how to determin if a tack is bad by trouble shooting the device it self. If that makes sence, I want to eliminate all other componets. But I cant find instruction on how to do that.

 

[BaileysBoat]

Re: How to trouble shoot a tach

Tach must be grounding the coil negative. What is the resistance through the tach to ground. Should be very high.

 

[solar7647]

Re: How to trouble shoot a tach

Tach must be grounding the coil negative. What is the resistance through the tach to ground. Should be very high.

That is what I am thinking, I wont be able to test until Friday. I am trying to get as much as possible as far as information so that I can do the testing.