I have a 98 expedition 4x4 5.4 L . I am having problems whenever it rains. The speedometer doesn't work or works erraticly. The defroster fan sometimes stays on after the key is shut off. ocassionally the 4x4 indicator hi low all light up. I have also heard a strange sqealing sound coming from under the dash near the glove box. I haven't found any wet carpet but it only seems to happen when it rains so something is getting moist. Any ideas would be greatly appreciated.

 

Wecome to the boards.
I recall seeing some posts some time back about leaking windshields on the passenger side getting water onto a computer mounted under the dash. It caused all kinds of problems but I can not recall what they were. Try doing some searches in the electrical section and you should be able to find more info.

Good Luck