Electrical issue...

[SonnyAK]

we have a '90 FJ62 that has acquired a radio issue...Here's the back story. Recently it started running poorly when my girlfriend was driving it and she said the voltmeter spiked all the way to the top and then way low. It kept running but was slightly rough. I drove it and the battery light, brake light and trans temp lights were on. The alternator was shot so I just replaced it and the battery seems to be holding a good charge so I haven't replaced it yet - but it is 6 years old. After the big power spike, the clock went out, the radio wouldn't work, no interior lights, no parking lights and the power locks didn't work - maybe some other things but I remember those . A fuse had blown (I believe for the interior lights). Replaced that and found a burnt wire coming off the battery positive. This truck has 2 fuseable links and another wire off the positive, and the single wire was broken. Spliced in a similar size wire and now everything is working correctly except for the radio. It comes on but only has static and when I shut the power off (ignition or radio power switch) the info on the screen goes out but you can still hear static and the backlight stays on...What do you all the think?? I'm an electrical idiot so any help is greatly appreciated!!

 

[60 toy ota]

Seems to me like that other wire should have also been a fusible link, and had it been you wouldn't have gotten a fried radio

 

[SonnyAK]

I would have thought that too but looking at the wiring diagram it only shows 2 of them on this model and a single wire direct to the starter. Im not sure what the purpose is of this wire since the starter will still engage as normal so it's not that wire.

I drove it today and everything went well for a while, but when I started messing with the radio, the same wire as before, burned through and the same items lost power (locks, interior overhead light, clock, radio). When I got home I checked and the to see if the same wire had broken, and it had. It's attached to a much heavier wire and I'm assuming I'ts designed to do this?? During the drive the radio would play some on AM but had poor reception. The sound level is normal on AM but when switched to FM the level drops way down. It popped a bit louder at first through the speaker and I assume that's when this same wire fried again. Very odd for sure!!

We've had this truck for 2 years and everything has always worked properly until this issue and it's completely stock with no aftermarket wiring that I can see. Thanks

 

[SonnyAK]

In case anyone has something like this pop up on their 92, here's the outcome. The wire that burned through does act as a fuseable link (goes to alternator and a few other electrical items). I took it to a local shop to figure out the issue and they said the wire I had used as a replacement wasn't heavy enough (needs to handle 50 amps) so they replaced it with the proper gauge wire. The radio is still inop and they unhooked it to prevent a draw. They said the factory radios were usually the most fragile item in the electrical systems and are very suseptible to damage from a quick spike like this had before the link went. Everything works as it should now but I'll have to replace or repair the radio if I want that working again.