I have an electrical gremlin in my truck. It seems to happens when there is a strong rain storm. It seems water is getting in under my dash or behind my fire wall (I think don't have proof). The end result is my truck battery is drained. The symptoms are odd... last night my wiper control only worked when the truck is in neutral or park. When the truck is in park I could set the wiper speed and shift to drive... the wipers kept wiping but I could not change the speed or shut them off. To shut them off I need to turn to Neutral. Also the automatic climate control kept itself on after the truck as been shut off. (I'm thinking that's what drained my battery); the blower fan kept running. The radio also only works if the truck in in neutral or park. Like I said we had a very heavy rain storm and I'm wondering if there is a leak in the windshield and something shorted. This morning the wipers worked in all transmission positions, so did the radio. When I got to work the wipers were once again not working when in gear. Today is didn't rain and it warmed up; on the way home the wipers worked in gear and so did the radio. When I shut the truck off the blower shut off as well.... everything back to normal. So I, wondering if there is a relay board that controls these functions and if anyone knows of areas the expedition could leak? Thanks for everyones help.

 

Leaking windshields are a very common issue that wreak all sorts of havoc on the electrical system. Turn your blower on high, on any selection except Max A/C. Then close all of the widows and doors. Now spray the windshield with a water hose and look for air bubbles. If you see any, then the windshield has to come out and be re-sealed.

 

Water is probably getting to the GEM box under the dash by the steering wheel. This box is the main I/O controller for the truck. My problem was the same after heavy rains .. and weeks after. See the water gets in to the box causing long tern and some permanant problems mainly due to contact corrosion. My water was actually coming from the moonroof. The moonroof has 4 drains one on each corner. The one on the from driver side was pinched of by wires going to the center overhead console. The roof never got wet. The water just went right down the inside of the pillar.

 

I think I got it narrowed down to the fact this if this is a leak it's coming in from the top. I don't have sun roof so that most likely means my windshield or I'm getting a leak through the air intake for the vents in front of the windshield. The first time I had an issue was months ago after driving to the airport in a downpour, got back to my truck after being away for a week and the battery was dead as a door ****. To add to the frustration I had an aftermarket ignition key (which I got when I bought the truck) that either got decoded or the loss of power also resulted in a loss of memory in the trucks ECU. To make a long story short I had it towed 60 miles home $$$$ only to figure out the next day that my OEM key started the truck. I had gremlins for weeks after with the battery draining and finally dying after sitting for a few hours. Knowing that a low battery can cause electrical issues on it’s own, I put a new battery in and my problems disappeared! Until this week that is… Thank you for the valuable feedback.