My 98 Expedition is possessed. Mechanically, it has never given me any problems, but has had electrical problems since new. Latest problems include: rear window wiper quit for good, radio and a/c fan turn on by themselves w/o the key (this tends to run the battery down overnight), air bag light on (used to go out occassionally, now on for good), tried to start itself w/o key one rainy day (had to unlock the door with the key, fob didn't work) to unlatch the hood to disconnect the battery, the reading light, glove box light, and hood light quit working but the fuse is good, and occassionally the speedometer quits working while driving the vehicle causing the trans to shift erratically. Next day it works fine. Wish I could afford to trade this monster off. Any ideas, could all or most of this be caused by the same thing?

 

This is what happens when it catches you eyeing Yukons in the GMC showroom.

A guess: A bad GEM (General Electric Module). Do a search on this site of "GEM".

 

Sounds like the old leaking windshield into the fusebox and shorting trick. Was a big problem for a couple years.

 

Thanks. I tried a search for GEM and General Electrical Module and didn't get anything. I know GEM is mentioned a lot so the search feature must not work properly this morning. Where is the GEM located on the Expedition and is this something that is costly and difficult to replace?

 

The Gem is monted on the back of the fuse box. You dont necessarily need to replace the GEM. What is happening is that the water leak drips down into the fuse box assembly and creates power shorts causing lots of electrical malfunctions. If left long enough then the contacts get rusty/corroded inside the fuse box and often you will need to replace the fuse box. The Gem may be fully functional, but you will have to test it all after cleaning and drying out the fuse box, or replacing the fuse box. Fortunately Ford made the fuse box removable from the main loom, or the whole harness would have to be removed like on older models.

It is located on the driver side of the instrument panel on the 98. You will have to unbolt the two large bulkhead connectors at the back of the fuse box, then remove the bolts retaining the box to the dash. You will also find up to three connectors attached to the GEM module which are clip locked into place that will need to be disconnected. The fuse box has a retention clip on the face of it you release as well. Then you just have to worm out the fuse box and GEM as an assembly out of the dash.

Then you can inspect the pins at the back of the fuse box for corrosion and water where the two 40 pin connectors were removed.

The most important thing to get done after you repair it is the windshield leak problem or it will continue giving you the same problems.

 

Great advise. I will take a look at it, and thanks.