16-pin 5-wire OnStar Rearview Mirror Harness
I'm replacing the factory OnStar rearview mirror with a Gentex auto-dimming+compass mirror. Instead of wiring the new mirror into the dashboard, I am trying to wire it to the existing OnStar harness. The 16-pin harness has only 5 pins in use: 8 (black, gound), 11 (blue), 12 (black/white), 14 (grey), 15 (brown/white). The black/white wire controls the OnStar button illumination (green LED light), so I think I could use it as the source of the new mirror.
However, the wire's voltage is strangely 10V. So I got a voltage converter to make it a 12V. The strangest thing is then followed: although the voltage of the wire is 12V according to the multimeter, it can never power on the new mirror. The new mirror is also functional: it works when wired directly to the battery. Hard to understand why it's 10V and why the new mirror fails given a suitable voltage.
Any thoughts on the OnStar harness and other physically nearby wiring options?
Last edited by OwenS; 05-29-2018 at 08:50 PM.