90's explorer 4wd troubleshooting

[NotMatt]

So, my girlfriend has this 92 explorer that she needs to get rid of... problem is, the 4wd isn't working and in these parts at this time of year, that's gonna be a deal-breaker for a lot of people... so I told her I'd fix it so she could sell it. Problem is, I don't really know what I'm doing on these rigs.

The rig has manual hubs and push-buttons for 2wd, 4x4 and low range on the dash. When I press the button for 4x4, it doesn't light up, and nothing happens, 4wd doesn't engage. I understand there's a process for low-range, IE foot on the brake, trans in neutral, etc... tried that for low and it doesn't do anything there either (no lights on the switch or anything).

I pull the trim off the driver's side rear and found the 4x4 "computer" thing... unplugged the connectors and pressed the reset button, the LED flashes 4 times, and then I plugged everything back in and same result. When I press the button on the dash, I can't hear any of the relays in or near this computer click or anything... so my best guess it that the switch is bad or there's a fuse out maybe?

I read about the process for rebuilding the shift motor, but I'm not ready to dig into it that far until I can hear the relays click when I press the button, since nothing's gonna happen anyway if that doesn't happen first.

Anyone whose worked on one of these have any tips? I know we have a few Ford guys on here... Somebody HALP! I want this thing out of the shop so I can work on my Jeep! :redneck:

 

[zukkev]

Make sure the motor on the t-case is plugged in, and that it has a good ground, otherwise nothing'll work! :redneck: You should also be able to grab a schematic and use a test light to make sure the TC comp is getting power...my guess is it is, since pressing the reset lights the led..

 

[NotMatt]

Yep, it has power/ground at the computer... I'll check the connector at the shift motor tonight.

How common is it for the dash switches to go out on these?

 

[Totalled]

Never. Start at the shift motor.

 

[Dogboy]

The shift motor went bad on mine, then about a year later the actual shift computer went bad.

In the shift motor, there is a little rubber bushing that, over time, gets squished, and allows the motor to turn passed where it is supposed to. At which point the computer "loses" where the motor is, and can't make it shift anymore.
I pulled the motor apart, and crammed a piece of hard rubber house around it, and it worked.

As for the computer, there is a button on the top, and if you push it, the LED will tell you if the computer is working right. I can't remember how to read it, but it's simple. All the code says is it either works or it doesn't.

 

[NotMatt]

Well, just to update... I never fixed it. The 20 amp fuse under the hood was good, the 15 amp fuse under the dash was good, the computer was good, but I didn't get far enough to take the shift motor off... sold it on Saturday for 500 bucks and that's the end of that! :redneck:

 

[CHOP SHOP]

I was gonna offer help. If you were still having trouble shooting it, I could come over and shoot it for free. No problem!

 

[NotMatt]

I was gonna offer help. If you were still having trouble shooting it, I could come over and shoot it for free. No problem!

After the first few craigs flakes, I almost considered that option. I love the sob stories, payment plan requests, no-shows, and trade offers you get when you're selling a 500 dollar rig.