You have a ground wire problem somewhere. Start with the large ground wire on you battery and make sure the connections are not corroded and are tight. Next check around the engine compartment at the wire bundles and make sure the ground to the body or frame are making good contact. One of those two items should fix the problem.
Fuse #9
A faulty bulb?
Check fuses , or bulbs in radio burn out.
Bad Battery. Bad Alternator. Lights left on by mistake. Something left running. Exc.
When you hit the bump, the mouse wakes up.
I had the same problem with a 1999 Expedition and it was a bad plug. Ford had a problem also with the plugs blowing out. It cost me about 1200.00
check this link; http://www.aa1car.com/library/us1296.htm
will the transmission causes my 1999 ford expedition to bog down & sputter when accelerating the 4.6liter engine.
Are you sure you didn't turn the dimmer down
Check your owners manual. If you don't have one copy & paste this link. http://www.genuineservice.com/genuineservice/en/gloveboxresults
Expedition Journal - 1999 Into the Blue was released on: USA: 1999
where is located ford expedition 1999 relays