tach on/lights off, lights on/tach off - WTF!?

[66gtk]

Just like the title says - when the lights are off, all is working well, and when I pull on the light switch, the tach dies and I have no tach light like I used to. The rest of the guages work fine, but the pod is wired seperately. Any ideas on where to look now?

[Video_Master]

redo the wiring for the tach. Sounds like the wires are messed up for it.

[CobraReborn]

Ya sounds like the ground and light might be switched around

[66gtk]

Yea, but I didn't touch any of the tach wiring or underdash wiring, except where it goes onto the coil. Of course, the oil pressure and water temp gauges are in their respective places correctly...