Sounds like a bad ground from what I've read. I'd start there. If all grounds check out good, I'd have your alternator checked. We drove an Expedition on vacation a few years back and as we were pulling into the hotel, lights were flashing, doors were locking and unlocking, radio was intermittent, just random things happening. It could be going out.

 

Added some pics, I wanted to keep all of them on an old page so I edited my last post with the pics lol.

 

Where would the other grounds be? I've checked out the one stud right next to the batter (I put a picture of it in another post), but I don't know where any others are.

Right now it's just the radio is not working and the turn signals are kinda screwy. Not sure if they're related or not, but I'm just going to take it to get the truck scheduled in to a shop tomorrow and I'll have them check out the alternator and hopefully fix the issue.

 

Easy way to tell is to run a good ground wire to HU and try it
Or check resistance to ground on its chassis with a multimeter
Just touch a good wire to the chassis , its all grounded. you dont need to connect to its ground wire.

Does it have a fuse on the back of it ?

 

Also, check to see if the illumination wire on the radio (orange or orange w/ white stripe) has gotten into something. IIRC, our trucks don't have an illumination wore from the harness, so the illumination wire from the radio isn't used. Make sure that didn't get into anything.

 

In your second harness picture with the 8 wire connectors (some Fords used 5, some 7 of the 8), you will see the solid black wire (the sixth slot, but 5th wire on the truck side of the harness. I always count it as the 5th wire, since most don't have other wires in the harness, unless it's a Navigator or Lariat with CD changer. That black wire is the chassis internal ground wire. It is the 6th wire, still black, on the radio side. The antenna also grounds the chassis, so it shouldn't be a ground problem with the radio. There is mostlikely a blown capacitor in the radio, causing no sound.

I've been running into this since I started working on Ford navigation systems and such. I've added navi to all my cars and trucks, using factory heads, and rewiring the plugs to accept steering wheel controls and heater controls. I've done numerous newer Mustang's and did several write ups on how to add swc's to Fords without factory wiring.
on Mustang forum's and another F series forum.

When I pull apart some of the aftermarket heads, that were removed from some wrecks, I've found that Sony has the best internal components to reuse. The JBL Sanyo, and other lesser expensive radios, have very weak, cheaply made components. Kenwood and Alpine have some really good parts, but some very weak electonics inside them also.

This is how I've been spending my winter. Tearing apart electronics and making up security systems out of the parts. Most items work fine, but some of the stuff is just truly junk and can't be reused for anything. I don't know your radio brand, but this could certainly be youor problem. Do you have the old radio to plug in and try? That would help eliminate your choices. Good luck.

 

I would check the speaker output from the radio head itself. I would use a house speaker, something you can run wires to. I would use the two purple wires. One has a black stripe on it. That is the negative for that speaker. The other is the positive. I would clip it and run leader wires to the speaker and see if I had sound.

This way you can eliminate if its in the wiring through out the truck or at the head. It looks like an older head unit and it is fully possible the sound portion of the logic board is just done.

 

I don't have the old radio, it came with this when I bought it. No idea what brand it is, this is what it looks like:




The truck is off so it's not illuminated, but when the truck is on it still illuminates, I can change between radio, aux, and CD. It will spin and play the CD, but no sound. I can change radio stations, but again, no sound. The antenna is grounded properly, but IDK about the 5th / 6th wire you're taking about, I'll take a look at that in the morning. Where does it ground to, any idea?

I just got the alternator tested, and it's still good, so I have no idea where to go after this. I'll take the truck to a mechanic hopefully tomorrow to see if he can find anything wrong electrically (mainly to fix the turn signal), and if he can't fix the radio, there is a car toys right next door I'll probably send the truck to.

Another thing I just remembered is that the right half of the radio buttons never lit up, it faded out until none of the lights on the passenger side where on. The screen was illuminated right, but the buttons on the face of the aftermarket radio wouldn't fully illuminate if that makes sense.

 

Anyone have any ideas what this blue wire is supposed to do? I'm half tempted to try and ground it but it's blue, not black lol.

 

Blue is usually the power antenna or amp turn on. Don't ground it.