Re: 1994 s-10 electrical help needed

earl wrote: 
The original problem was rear view mirror switch was bad.  After
replacing one, and it immediately blew, I started to check. Turns out
that I am getting power to the outside rear view mirror switch from 2
power sources, where it should be only one. If I remove only the fuse
for the power mirror circuit, I still have power to the switch.  If I
remove the courtesy light fuse only, I still have power.
I checked last night, and I believe I am getting power back fed into
the circuit from the dome lamp.  If I remove the dome lamp, all is
well. If I install the dome lamp, I am back to two power sources to the
mirror switch.  Interesting note to add, the reading lamps on the
inside rear view mirror do not work from the switches on the mirror.
They will go on with the door open, but with door closed, and after the
timer times out, you cannot manually turn them on.
Back to your question, the dome lamp should come on when the door is
open, or with the dimmer switch on the dash. And no, the other interior
lights behave correctly.
I am still tryin' and I do appreciate the replies!!!!


Normally the wiring that goes overhead goes up the A-pillar. Im guessing it does that in your vehicle too. There is only need to bring a single ground overhead.

I don't have the schematic so im going off general knowledge here (automotive systems engineer for 10 years). The dome lamp and the mirror lamps are both connected to ground through the ajar switches. When the ajar switch is open (door closed), you essentially have +12V on both side of bulbs. Since the other side of the mirror bulbs is the dome bulb, this will look like two sources of power, but its reall not. Try checking when the ajar switch is closed (door open).

Technically if they share a ground they should be from the same Fuse. If its not then its a bad design, but thats beside the point here. Maybe you can double check though that the two appearant power sources are from different fuses.

Also power mirror fuse likely is unrelated to rear view mirror feed.

You should have 3 wires in your rear view mirror. One is 12V from a B+ fuse. One is a ground. One is tied to ajar/dome switch. Check that each of these is working.


I didn't follow your statement about what happens when the dome lamp is installed and it being dim. Did you mean to say when dome lamp is installed the mirror lamps lit dimly?


It looks to me like your problem is the ground wire to the rear view mirror is cut, or maybe a terminal has pushed out of the connector. Or maybe its another bad mirror switch.

--
Thank you,


CL Gilbert
"Then said I, Wisdom [is] better than strength: nevertheless the poor man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16
.

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