'98 Ford Expedition - 4WD/AWD won't engage.

The switch to engage the 4WD/AWD does not light up and the 4WD/AWD will not engage.

No engaging noises or anything. It's as if the switch has disconnected itself from the rest of the system.

The transmission seems to function normally in "Drive". No slippage or strange noises.

I visually checked the following fuses according to the owners' manual and they all look fine:

UNDER DASH
5 - 5 amp
6 - 5 amp
7 - 5 amp
17 - 10 amp
23 - 10 amp
24 - 10 amp (I thought this one or #23 would be the problem)
29 - 5 amp

ENGINE COMPARTMENT
17 - 30 amp

Is there possibly a simple solution for this problem? A fuse I'm missing? The switch itself? It seems like it's electronic in nature rather than mechanical.

Possibly related - maybe not: The heater has stopped blowing hot air through the front vents. The rear vents work fine. These problems seem to have started at roughly the same time, so I thought they might have something to do with one another.

Thanks in advance for any advice you can offer!
H. Eric Mayse mayse@optonline.net

 

First stop is always the fuse then the switch. After that, since the indicator isn't lighting up, the module that controls everything. That would take a scan to determine.

 

unfortunatly common problem with non mechanical shift 4wd systems, usually caused from sticking actuaters not moving the shift mechanism in the transfer case, ford usually uses electric acuators, gm vac both have problems as they age, you will need to check the connections at the trans and see if power is actually getting to the actuator. see if autozone has an online wireing diagram.

life begins when the kids leave home and the dog dies.

 

Holy crap, I didn't expect such quick responses! Thanks guys!

I'll look into the things you mentioned next. Hopefully I'll get some time for it this weekend. Thanks for the info!

-H. Eric Mayse-

 

more than likely its the shift motor, I have changed plenty of them

 

If it were the shift motor, would that also cause the switch to stop lighting up?

That's why I thought the problem was more likely something electrical rather than mechanical in nature.

-H. Eric Mayse-

 

to the best of my knowledge yes.the gem module controls the ground from a signal it gets from the transfer case positioning lever.
good luck

 

Got it. Okay, thanks for all of the great advice, guys!

I've already recruited a couple of my sons to help me try to figure it out this weekend, so if the weather's nit too awful (New Jersey - so chances are it'll suck ), hopefully we'll get to test some of your theories.

I'll let you know what happens. Thanks again!
-H. Eric Mayse-

 

Well, as fate would have it, the day after I posted that last message, a tractor trailer side-swiped my Expedition and completely demolished the whole passengers side of the truck. No injuries, just some hot tempers.

It was their fault and the insurance company's calling it a total loss. For the amount of money they're giving me, it'll be easier to just go and buy another used Expedition, sell the one I have for parts, and use the extra money to wrap up any minor issues my new purchase will have.

So, needless to say, I'm not going to bother fixing the 4WD on my Expedition now. Thanks for all of the advice! Sorry I couldn't make better use of it.

-H. Eric Mayse-