2005 Excursion Limited 4x4. Will not go into 4 wheel drive. At initial key on the 4x4 indicator light comes on briefly.
Tried manually locking the hubs, no 4x4.
Tried swapping the underhood relays around, no 4x4.
Should I be looking for voltage at the transfer case 4x4 motor to determine if it is faulty when turning the in cab switch to 4x4? I'm thinking that would tell me the transfer case motor is shot, I think.
Thanks

 

I found a bad wire to my motor when mine didn't work.

 

You have two things to look for on the transfer case. You have the motor, and you have another plug on the other side of the case that reports back to the computer what position/status/state the transfer case is currently in. If the computer doesn't get a report as to what the transfer case is currently doing, then it will not command it to go into 4x4.

I have also seen a transfer case fail to operate due to bad wiring. Bad wiring meaning compromised, broken, or corroded wiring. The conditions down there could not get much worse for wiring to endure. Mud, salt, water, heat, cold, etc. From my experience, the wiring will be bad inside, or right at, the plug. Pinch the insulation and make sure it has not corroded away to a green powder. Seen that before, too.