Tach jumping while ignition off!!

[pistolpete]

I am in the process of figuring out electrical issues on a car I bought in pieces.
The tach was out of the car when I purchased. I installed it and the left blinker is acting wonky, When the ignition key is on the tach is bouncing without the car running. Also sounds like feedback through the speakers but I cannot hear it out of the speakers.
Left blinker is flashing fast when on.
Please send me your ideas.

[pistolpete]

It is hapening when the lights are on

[silverlock]

1. What car?
2. How is the tach wired? Photo? How do you know it’s wired correctly?
3. What have you tested so far?

[pistolpete]

Sorry 1986 911
I think it is wired correctly but maybe not.
I have a photo of the back of the tach before installed.
I can get one of it wired tomorrow.
Have not tested anything yet I was stumped.

[pistolpete]

[Hi_Fi_Guy]

My ‘71 911T recently experienced the bouncing tach with engine off but key on too. It’s baffling.

[EC900]

Looks to be a 1988 tach based on the date stamping.
Someone will have to chime in if the wiring is different from ‘86 or even these are plug and play interchangeable.

[pistolpete]

[pistolpete]

I could not get great photos but hopefully this might help