I own a 1994 Toyota Truck with factory installed stereo. The stereo and front speakers work but the speakers in the back seat never have. I am not the original owner so I do not know the history of the stereo system. I've never attempted to replace or repair the rear speakers. For the second time since I've owned the truck, the wires to the stereo and/or speakers have burned up. The first time wasn't so bad and I thought I'd pulled out the offending wire. This time however, it was much worse. A wire burned up to the point where all of the insulation completely melted away, burned up parts of the carpet, and melted the radio fuse in the fuse box. There's a wire that runs directly off of the fuse box (from the radio fuse), under the carpet, and into a side compartment in the back seat where one of the speakers was. It was not hooked up to the speaker or anything else. This is the wire that burned up really bad this time. Question 1: Why would the wire that came directly out of the fuse box need to run to the speaker (apparently)? Question 2: Everything else (electronically speaking) in the truck is running fine, but I'll probably need to replace that fuse box. Is this hard to do?
Some of the premium stereos had a separate power amplifier mounted under the passenger seat, or they could have hid it in the rear quarter panel of the cab where you found the wires heading.
The remote amplifier would get you some serious volume from the radio, levels where they couldn't get rid of the heat behind the dash
- or they'd be cooking the CD's or Cassettes being played in the head unit. Those stereos used a special adapter cable that plugged into the factory wiring harness with a standard radio receptacle, and then plugged into a special connector on the back of the premium stereo. The special harness went under the carpet and plugged into the remote amplifier.
If that factory premium stereo system died destructively and damaged the wiring, they could have yanked that premium stereo and installed a another stock radio that didn't use the remote amp - but they left the power fuse in for the remote amp and it appears the damaged wiring grounded out again.
If that's what they did, simply leave the fuse out of the fuseblock. But because someone will see the empty fuse hole and try putting another fuse in again later, the best move is to snip and insulate that wire on the back of the fuseblock. This way it can never ground out again.
You do NOT want to go there... ;-) Royal pain in the (butt), those main body wiring harnesses can easily top $1,000 new and take days to swap out, they stop at 50 different components and switches on their way through the car, you have to gut the whole stupid dashboard to get it out...
And a complete harness won't be much cheaper at a junkyard, because they either have to pay a worker to remove it in one piece, or you'll have to go to a "Pick Your Part" yard and spend a full day (or more) extracting it yourself.
If you don't absolutely have to change the whole harness - and since you say it runs fine and I'll assume all the gauges and lights work properly - just fix the old one.
Disconnect the battery, pop the fuseblock loose, get access to the back side, and patch up all the insulation on the few wires that you can see are overheated and damaged. If the damage goes inside the harness sheath and down the harness, you might have to unwrap it and extract the burned wire, patching all the ones it melted to on the way. If there's a LOT of damage inside the sheath, now you know you'll have to replace it.
Then replace the outer wrapping on the harness like you found it, or it can chafe through and short out somewhere else. Several rolls of electrical tape, a bunch of black Ty-Raps and a few yards of the split corrugated wiring loom cover later, and you should be back to normal.
Wow! Very thorough response, Bruce! Thank you for taking the time to post that extremely useful info.
I was hoping that fixing this would be as simple as getting a new fuse block and wiring it up to the old harness(es) (the undamaged one for the other vehicle electrical components).
I'm taking my truck tomorrow to a shop that specializes in electrical systems. I'll ask the mechanic to check out the rest of the vehicle's electrical system and harnesses for other damage caused by these burnings. Then I'll ask him to pop the fuseblock and patch up all the insulation on any wires that are overheated/damaged.
Hey, I hope it's simple for you, too. But life isn't always kind.
The last time I had to fix a main body harness was on a 1962 Dodge Dart that a friend totally shorted out, and rather than fight with fixing the old one I just made a brand new harness for the whole car. Of course, that car had about 35 different circuit wires total, between the battery hot wire, ignition, gauges, horn lead, dome light, headlights and taillights, etc. Took a day to figure out, round up the needed wire colors and sizes, breadboard (sheet of plywood and nails) and build, and a day to install, hook up and get the car running.
Modern car harnesses with electronic fuel injection, lots of sensors monitoring the exhaust and engine systems, fancy climate control, factory cruise control, can have 300 to 500 different circuit wires going back and forth - with several big 60 or 100-pin bulkhead connectors, and several splices and diodes buried inside the harness to boot. It takes a triple dose of patience to fix them.
You do a bit of digging - if the damage is slight, fix it. If the whole thing is toast, no sense wasting a lot of effort on fixing it, swap it out.
Good move - these guys see it every day. And they know the difference between slightly toasty (fixable) and Extra Crispy (fuhgeddaboudit). ;-)
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