2004 Ford Excurison XLT 4X4 V-10 Gas 6.8 L 102000 miles. We bought this SUV to replace our 1998 Suburban ( 346000) miles on it.
We get home and a neighbor says, you have "no tail lights, or parking/marker lights, but the headlights worked, along with the mirror marker/turn signals. Ford dealer checked, said the headlight switch was bad. I replaced the switch and still no "parking lights!"
I found the diagram and run s new wire from Switch to L fender under the hood. I hooke this wire to a 30 amp circuit breaker. Then I run a new wire to both front parking lamp/side markers. I then run a new wire to the rear Tail/parking lights. This resolved the "No Lights Problem.
A week ago we were driving and my dash gauges quit working. Then I saw the 'red battery lite was on. Confident the Battery was good, I bought and installed a New Alternator (Rebuilt). Had a good Samaritan waiting to see if it would start, it started up and no problems. The truck was driven more then 120 miles and as I was making a Left Turn, all the dash went out, gauges, speedo and tach, radio stopped, windows would not work. No problem driving, and the a/c was still working. We had gone about 35 miles and made a Left turn, everthing was again working. Went home and checked the belt, alternator, Battery and connections. All were good.
Next day got in the truck, started and "all" was fine, drove for about six miles and "All" gauges and such come on, then went out. Truck was running fine, a/c fan was blowing, so I drove to autozone and had Batt, and Alt checked, both were good. I get into the truch and pull out of the parking lot, as speed increased all gauges went out again, now as I stopped they come on radio and such worked.
It appears to take a few minutes/5-6 miles driving and it does it again, take off from a stop and as you get up speed truck runs, but gauges flash and all go out. You stop and they come back on. I start, they go out on forward movement, come back on as you stop?
Hope this drives you as "Nuts" as it has me.
First of all check the smaller battery cables, particularly the positive one where it bolts to the under-hood fuse box. Be sure that is tight. Also check the negative one where it bolts to the body.
Running new new wires is not the way to fix a problem unless someone cut the insulation and the whole piece is corroded. I never allowed my students to do that. The proper thing to do is perform a series of voltage tests to identify the break, fix it, but most importantly identify WHY it broke. If a wire was rubbing on a sharp metal bracket or laying on a hot exhaust part, it is only a matter of time before the other wires in that harness will suffer the same fate and you will have to start troubleshooting all over again. When you finally get a professional involved he is going to disconnect some things so he can take measurements, and custom, add-on wires that he doesn't know about will seriously confuse the issue and cost you a lot more money for his time. I was involved with one in particular that would have taken less than an hour to find but the owner was not aware that someone previously had switched two wires in some misguided attempt to "fix" something. The result was well over 30 hours over nine visits before I figured it out. Once the cause was located, (only three feet away from where someone cobbled the wiring), it was easy to see why it had the symptoms it did, and luckily the owner was very patient, but all that aggravation could have been avoided it the first person had just diagnosed it properly and fixed it right.
You also have to understand that Ford's insane engineers have gone out-of-control with designing in inappropriate technology that adds unnecessary complexity to their vehicles. In this case the instrument cluster is the most intelligent, (complicated) computer module on the vehicle. They don't do anything that other vehicles do; they just add a computer to the circuit, and computers in that environment are very unreliable. Road and engine vibration degrade electrical connections. Body flexing over bumps in the road and when cornering put varying stresses on electrical connectors. You can expect to be chasing electrical problems forever. Mechanics and others who understand that throw up their hands and run out of Ford new-car show rooms where they promote all that technology as something to be desired. We all know the problems that are going to occur and the frustration and expense that will result.
There have also been a real lot of problems on Fords associated with the "GEM" modules. That is their "Generic Electronic Module" which is their name for the Body Computer. I've never been involved with one myself but I hear and read about them all the time. Most problems come from water leaking past the windshield and dripping onto the computer. It is involved with the things that never needed computers before like power windows and locks.
You also have to consider loose terminals on the connectors on the back of the instrument cluster. This is becoming more common on all vehicles now that they are all computer modules instead of simple gauges and lights. If it looks like the cluster is involved in the problem you will want to get the dealer's repair department involved. The anti-theft system is partly incorporated in the cluster. The cluster is even one of two computers involved in blowing the horn. It is the most common cause of a dead horn, and that repair generally runs around $800.00. THAT is what we mean by "inappropriate use of technology". My ten-dollar relay works my horn as well as Ford's two computers. A replacement cluster will likely need to be programmed to the truck, and if anything doesn't work once it's installed, it's their problem and they will have to sort it out. The days of adding custom wiring, even for simple things like trailer wiring, are long gone.