1999 Expedition Gem module/fuse box
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Joined: Jun 2020
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1999 Expedition Gem module/fuse box
Hi all! I have a '99 Expedition and started having those weird issues going on such as, windshield wipers not working, headlights or brake lights not turning on, blinkers not working, heater turning on by itself, interior lights not coming on. I took the gem module apart and didn't see any sign of corrosion. The fuse box did, so I switched that one out with another one. Now, the only issue I have is that the main headlights and brake lights don't come on (I want to note that the dim headlights do come on), and the blinkers aren't working. I checked all the fuses and they're all fine. Also, I got a new battery for my truck since the old one seemed to be defective (didn't charge after attempting to charge it) and now when I try to turn the truck on, its not turning over. I know it's not the fuel pump cause I changed that out almost 2 years ago. Any idea what it could be or what else I should check?
Tuned
Joined: Nov 2008
Posts: 499
Likes: 87
From: Oregon
Hi all! I have a '99 Expedition and started having those weird issues going on such as, windshield wipers not working, headlights or brake lights not turning on, blinkers not working, heater turning on by itself, interior lights not coming on. I took the gem module apart and didn't see any sign of corrosion. The fuse box did, so I switched that one out with another one. Now, the only issue I have is that the main headlights and brake lights don't come on (I want to note that the dim headlights do come on), and the blinkers aren't working. I checked all the fuses and they're all fine. Also, I got a new battery for my truck since the old one seemed to be defective (didn't charge after attempting to charge it) and now when I try to turn the truck on, its not turning over. I know it's not the fuel pump cause I changed that out almost 2 years ago. Any idea what it could be or what else I should check?
As for your Electrical issues... Take The Time to find every single wire in your engine compartment and check that they are tight, don not check tightness by hand, check with the proper sized wrench on each nut of bolt that the wire is held down with. Also check all engine wires connected to the Engine Block (these would be ground wires mostly) and all the wires connected to the Starter.
Then get back to us.
More Turbo
Joined: May 2014
Posts: 642
Likes: 12
Hi all! I have a '99 Expedition and started having those weird issues going on such as, windshield wipers not working, headlights or brake lights not turning on, blinkers not working, heater turning on by itself, interior lights not coming on. I took the gem module apart and didn't see any sign of corrosion. The fuse box did, so I switched that one out with another one. Now, the only issue I have is that the main headlights and brake lights don't come on (I want to note that the dim headlights do come on), and the blinkers aren't working. I checked all the fuses and they're all fine. Also, I got a new battery for my truck since the old one seemed to be defective (didn't charge after attempting to charge it) and now when I try to turn the truck on, its not turning over. I know it's not the fuel pump cause I changed that out almost 2 years ago. Any idea what it could be or what else I should check?
Headlights are Main Switch---Dimmer Switch---Lights
Brake Lights and Turn Signals both go through the Flasher Module. The Brake light switch just makes it "stick" on bright in the rear.
What's the common thread here? The Multi-Function Switch. It houses the headlight Hi/Lo dimmer switch, turn signal switch, wiper switch, etc.
After going through my entire truck to make certain the entire ground system was in proper order and still getting no headlights, I traced the circuit back to the Dimmer Switch. Ordered another Multi-function switch from Rock Auto and while I was waiting, cracked open the old one. Burnt, fried and heavily corroded. The contacts for the headlights' high and low beams were charred beyond salvaging because all of the power for the headlights goes through this switch.
Soon as I got the new switch, I retrofitted relays into the harness under the air filter. Switch can't cook itself if it's only passing 500ma instead of 10A.
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