sun tachometer problem

I have a Sun tach that I purchased 11 years ago for my 66 nova. It rests on my steering column and has 4 wires coming out of the housing--the red connected to my fuse box, the green to my positive side of my coil, the black as a ground (attached to the negative side of my coil) and the white to my inner dashboard idiot lights...the tach works fine until I put my headlights on---then besides not having the light on within the tach, the unit does not operate at all and my dashboard lights periodically blink. I am thinking that the light bulb within the unit is bad, or I have a problem within the wiring harness or headlight switch. How do I get to the light bulb within the tach to replace it...thx russ

 

Welcome to the HAMB Lildrip.....However,,You have posted this in the INTRODUCTION forum page,,,READ the "sticky" at the top of page...INTRODUCE YOURSELF as Ryan requests...Then post this in the main message board....

 

what he said!!

 

HI, If you want to send it to me I'll fix it it If I can't there is no charge.. I will consult with you before doing anything. only charge would be shipping if I can't fix it. e-mail me at catclock@msn.com. and I will explain more.

 

It sounds as if you have wired it incorrectly. What model of tach is it? What control box (if any)?