Door Speakers Do Not Always Work -- NOT The Inner Door Wiring!?

[Metalface]

So here's something silly. And it's very hard to search for here because you get results that talk about the door wiring. Maybe it's been discussed before, maybe not. Since this is a recent issue on a stock audio system, I guess I'll just have to let it slide and post anyway.

My front door speakers do not always work. They come in and out. I had chalked this issue up to being the "damned wiring in the door channels," due to posts on the forum, but I discovered something interesting today. I had noticed something this time since I happened to be paying attention -- the speaker was working totally fine until we parked, got out, locked the truck, and got back in. The front passenger door speaker was silent. "Aha," I thought. "I am a super genius, with 300 IQ, basically a living, balding incarnation of a God among other men," I thought. Upon turning the radio off and on, the speaker worked again flawlessly.
It never "goes out over bumps" or "works if you slam the door hard enough," it has to have something to do with the head unit itself. Wtf right? Has anyone experienced this? I do not want to lose my factory head unit, I love it. IMO (*and this is just for me, you do whatever you like*) changing out a head unit to a more modern one kind of *******izes the driving experience if you're looking for the 90s vibes. Not all are searching for that, but I am, so I wanna keep it all era-correct. That isn't to say I don't love modernized Explorer builds! They're all great!
So, I'd like to try to narrow down the cause by first hearing what others have experienced with their stock head units, then I want to try to fix it without replacing the head unit if I don't have to -- but I will if I have to and if it's possible, with another factory head unit. Mine is an XLT (a 97 XLT in Blue Lapis Metallic, with leather interior. Ladies and gentlemen please try to remain fully clothed.) and it came with the add-ons of the CD changer in the armrest pocket, but not the info center that sat below the center dash bezel. It has always done this, I removed the armrest and center console about 6 months ago, and it continues to do this. So that has nothing to do with it I am fairly certain.

What do now? Where do I put the JB weld and window screen?

 

[J_C]

Intermittent faults can be a pain to find. Do both front door speakers, always stop working and start working again at the same time? I don't know what to do with the answer to that, just thought I'd ask as that would be unlikely to be frayed wires in the door hinge boot.

The audio signal is low voltage AC. You could use a multimeter to determine if the signal is making it out the back of the head unit when audio is playing. You may need meter probes with needles or piercing type to make that electrical connection to measure it, if the radio wire harness isn't long enough to gain access with it pulled out of the dash.

If the signal isn't making it out of the head unit... wait, do you have the remotely located amp behind the cover pane in the right rear quarter of the cargo bay? If so then you can measure for whether the signal is getting to it, and if so, if it is making it out of it. There are multiple variants of the audio system in the 2nd gen wiring diagrams linked below in my sig.

Once you determine where the audio signal is stopping, then replace that part or do an autopsy if you have a little electronics diagnostic and soldering ability.

Depending on which head unit it is, there may be a few sitting on shelves at various auto junkyards. The rear amp, might be a little harder to find. They may not even realize there is one on a scrapped vehicle so it's still in the vehicle. Of course it could be a wiring fault instead, so you can just check for the low voltage AC signal from point A to point B and C, etc to see where it stops, though if both speaker fail simultaneously, a wiring fault (meaning probably two concurrent faults) seems less likely.

If I had to guess what is most likely based on what is presented, I'd guess that there's a single IC (amp chip) driving both the left and right front channels, whether in the head unit, or in the rear amp if you have one, and over years of time, it heating up in use has delaminated the circuit board trace(s) to it and/or broken the solder joints, so needs resoldered and possibly minor PCB copper trace repair. You could probably use something like standard 14ga solid core copper household wiring wire, to jumper from the amp IC to the next solid point on the PCB where the trace or power plane is in good condition still.

 

[yeahokay]

not a factory unit, but I recently replaced an aftermarket stereo and as I was testing the new unit all my speakers worked (they happened to use the same connector) I was planning on rerunning all speaker wire but turned out it was just the stereo in there that was broken. or perhaps the connector on the old unit was bad or dirty. Pull the head unit and clean it, it probably has 20 years of dirt built up back there anyways.