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2003 GMC Sierra Control Panel Issues

558 Views 19 Replies 2 Participants Last post by  Capt Jack
Fan works great but have lost inside/outside air switch, AC switch, and rear defogger with no LED lights. All circuit breakers, relays etc. test ok. Bought a new control panel, plugged it in.....same issue. Could be original panel failed and replacement (new model 599-210xd from Dorman) is also bad out of the box, but what are the chances? Any ideas as I really don't want to pull wire harness if I don't have to.
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Just to clarify your post is it the lights that don't work, or the switches?
So you have no power at all to the control unit.

I'd be looking for a blown fuse.
As I said in my first post, all circuit fuses and relays tested good (every fuse in truck tested by myself and 2 electricians).
Yep, I read what you said in the previous post.

The fan uses separate fuses (one if it automatic, 2 if it's manual speed selection).
All that proves is that the fan fuses are good.

Yes, it could be a wiring problem.
I agree it isn't the control unit.

Good luck
I've got some control unit drawings, nothing for the 2003; but the main wires should be the same, I'll dig them out tonight
Jack, the manual control unit uses 4 fuses, 2 are for the blower motor.
The automatic control unit uses 3 fuses, 1 is for the blower motor.

The 2 remaining fuses are the same for either unit.
There is an orange that is labeled battery.
And a brown that is labeled IGN 3

Both of those circuits are hot when in key on.
Jack, they might share a ground; but I see no reason to share a fuse
Jack, the drawings that I have only show the wiring connections to the unit in the dash.
They are named and they have colours, I don't recall if the pin numbers are there.

I can check for you; but home at the moment, will do shortly
Jack, bare wire shorts could cause transistors to pop.
Hard to say what kind of damage you may have.

I suspect new modules may require programing.
The engine size, the transmission type, etc needs to be the same and it may require that the serial number be correct.
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