4x4 switch

[toomanytoys]

The 4x4 in my 98 expy has stopped working so today I started to check some of the electrical. When I check the dash switch plug there are 4 circuits. The first is 12v hot when the headlight is on. The second one has 4.95v. The third shows ground and the fourth shows ground when the headlight is on. No matter which way I turn the switch there is no output on the third wire. Is this correct?

Does anyone have the wiring schematic for a 98 4WD system? The problem is definitely electrical as this happened during a Florida downpour. The lights on the dash started flashing and the relay kept clicking and after about 10 minutes it stopped. The self diagnostic lights still come on when I start the truck just like the airbag and check engine do. Any help would be greatly appreciated. Thank you

 

[1955moose]

It's possible, your gem module under the driver's side dash got soaked. Leaking windshields on 97-02 expedition is very common. My 2000 was a nightmare till I resealed windshield, and put dielectric grease in the plugs from Gem, and fuse box. I went through a downpour Thanksgiving night, here in Bay area, and no issues. When mine used to act up, 4 wheel drive light would flash, starter would engage while running, radio would quit, Etc. Seal your window, and do the plugs, it will be a huge difference.




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[toomanytoys]

I wondered about the gem myself but the 4WD is the only thing that doesn’t work. The rest of the truck is fine. I thought that when they got wet multiple things went haywire at once

 

[1955moose]

If your problem started after the rainstorm, something got soaked. I'm betting after a few days of dry out, all will start working. I have a wiring book for 2000 expedition, I can post wires for switch. Don't know if different.

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[toomanytoys]

This problem started during a downpour in Florida back in August. It still doesn’t work 3 months later. I just haven’t had the time to look at it but now I’m putting the truck up for sale so it needs to be fixed so it’s right for the new owner.

 

[toomanytoys]

UPDATE: After checking the circuits, relays etc I removed the cables from the battery and let the GEM reset. All is good again in 4WD land

 

[1955moose]

Sorry I didn't think about that. It's amazing how many members do just that, and seem to fix their problem. Glad you got it taken care of.

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