ELECTRIC QUESTION HERES ONE FOR YA

[XMAN JR]

I have a 67 GTX Factory console tach. My dad bought & installed a updated new circuit board in the tach. After I got the car I put in all new MSD dist. coil & box. The tach board instruction said all I have to do is take the tach coil wire & the MSD tach wire & splice them together. Great ! Well the tach works & has been working ever since. Now the question. Why does the tach stop working when I turn on the parking or the head lights ?

 

[greycharger]

insufficient ground someplace in the system is one possibility.

 

[bm02tj]

Tach is grounding through the lights in console
add new ground or repair the bad one