1986 International 1600S Wiring Issues

My 1986 International is giving me some wiring issues. Particularly with rear tail and marker lights. This truck plows snow and also spreads sand and salt for the town in which I reside. Some connections broke due to corrosion, which is an easy fix. Remove crappy butt splices and replace with heat shrink variety, but the thing driving me nuts is the directionals. Activate the right turn signal and the left flashes as well. Somewhat dim, but flashing just the same. Oh, did I mention that the marker lights are sort of doing the same thing? And to make things a little more interesting, someone has been messing around jury rigging all this wiring with those cheesy clamp on splices and electrical tape....GRRRR! Would someone kindly direct me to a wiring diagram so I might get this old girl back in order? I really don't want to have to resort to bringing it to a shop if I can rewire it myself. Thanks in advance for any assistance....

Sounds like you have ground issues first off. There may be a junction box in the back on the last cross member. That would be a good place to start. My advice if it has a junction box, unless it looks like new inside, get rid of it and start over. Haldex makes a really nice one, rubber inserts you can make a small hole to push wire through, also a rubber o-ring that seals the cover. You mainly need to verify that the light cord coming from the front is OK. Most truck bodies the wiring all originates in the back. After you find the harness coming to the back, a good voltmeter will let you know if the wiring is alright. Using the truck ground wire for your ground source, any less than 11 volts on any wire and you could have issues farther forward. I'm pretty sure the wires in the light cord are color coded and not numbered. White ground, Black and brown are marker/tail lights, yellow is left turn, green is right turn, blue is backup, if it has a red wire that is for trailer brake lights and/or electric trailer brakes. Good luck.

Thanks for your quick reply Shimmy. I was thinking along the same lines about the questionable ground as well. I'll look for that junction and track stuff from there.
Thanks again, and I'll keep this post updated....

No question in my mind the symptoms you describe come from ground problems.

An update on my little wiring campaign.....I was hoping for a quick fix, but that just never seems to work out for me. I forced myself to slow down and take a real good look at what I was actually dealing with. I found undersized wiring, taped up connections, those cheesy connections that pierce the insulation so you can add more crap that doesn't belong there.....I think you get the picture. I found the junction box that Shimmy directed me to located in the cab behind the driver's seat and found everything there in good condition. Traced the factory, 4 conductor cable along the chassis to the rear of the truck checking for any thing questionable. Everything seemed fine until I finally arrived at the rear of the truck, and that's where it looked like Mickey and Goofy took over doing the wiring. Needless to say, I clipped everything out and threw it where it belonged. In the barrel! Fabricated my own new harness providing power and ground to tail, turn signals and marker lights. Each junction carefully integrated into the line feeding it and then protected with adhesive lined shrink tubing. Time consuming, but I'm satidfied with my work, and the lights shine nice and bright like they're supposed to.

The Moron I bought my truck from used the crimp connectors and speaker wire to power everything. I have basically rewired the entire rear end of the truck since I bought it. Much better now that the lights work when they are supposed to!

Glad you found it, now you should no problems.....at that end anyways. I once bought a trailer from a guy who had done some "wiring" with dog fence wire and duct tape :beatsme

Glad I'm not the only one challenged with bad wiring. There's one issue I'm still having trouble with ant that is my back up lights. I'm only producing 8 volts for some reason. I checked the terminal at the junction box behind the seat and get the same results. Moved forward a bit and checked the connection at the switch on the transmission. I unplugged it and stuck in my probes and got a reading of 11 volts. Checked the terminals on the switch for continuity and all was good. Any ideas on why this is occurring? Trying to chase the wiring harness is a challenge as all the wiring is black. They have an ID # on them but it's not along the entire length. Only at terminal ends and even then the numbering is tricky.....