1974 18-plus clearance/tail light issues

[Ned_Slanderz]

New to the Forum and to the world of Chinook. I recently purchased a 74 Chinook 18-Plus on a Dodge B300 chasis. Has a brand new LA 360, and rebuilt a727 3spd. Mechanically and structurally it’s in great shape and everything works except the tail lights and overhead clearance lights.

I have read through the forum, but could not find much information about the older Chinooks. I know that the tail lights and clearance lights are wired off the trailer light harness. Only problem with mine is there is only 1 fuse box (6x 20a fuses) and I can’t seem to find where the lights wire into the fuse box.

I have checked all the grounds under the chasis and followed the harness from the DS tail light up to the cab where it goes up into the floor and up and along the B post then down the A post and into the the dash to the Headlight switch.

Brake lights, turn signals, hazards and reverse ALL work. It is only the taillights and clearance lights, oh and rear side markers…

Sorry for long story but I feel like this issue shouldn’t be as hard to solve as it’s been.

Thanks!
-Ned

[Ned_Slanderz]

[chin_k]

You may need to use a toner to trace the wire. Unless someone has chinook with the same year, it is difficult to figure out what they did without seeing the same model.

[Scott]

I sound like a broken record lately, but check your grounds. Always check grounds. Even if they're not the direct problem, they probably need attention regardless.

A lot (all) of the original Chinook wiring on my rig is not suitable for outdoor use. It's RV-level wiring, not automotive. The actual wire they used is nice stuff, but many of the terminations (wire nuts!!) are pretty lousy.

[Ned_Slanderz]

Thank you for the replies. I checked all the grounds and cleaned them up. Checked for continuity between all of the cleanse lights and down to DS tail light assembly. Everything checked out good but still no luck. When I follow the wires through the floor to the trailer light hook up it’s gets a little messy down there..

I checked all connections and traced the wires along underside of the van to where it goes back into the cab. Didn’t see anything that looked broken or brittle. Where the wires connect up into the cab I found x2 16ga wires (white and what looks like pink to me) that are not connected to anything and cannot find any loose wires underneath the van that run back to the tail lights.

If anyone has any idea what these go to I’d appreciate the help!

At this point I’m tempted to run my own wiring and relays for the tail lights and markers and throw a new switch in the dash.

[Scott]

Great! It sounds like you got in there and did some work. That's really what it takes (physically poking around).

Those spare wires could be anyone's guess in a vehicle this age.

Time, the elements, rats etc. can really cause some confusion, especially without schematics. I'd do what you mentioned and start fresh. It might save you time in the long run, it'll be more reliable, and you'll know exactly what's what.

[chin_k]

If you can easily figure out those two mystery wires' purpose, go ahead and see if they are powered, and you can control them with the light switch, but it maybe easier for you to just add in the wiring like you said. A lot of the older Chinooks are one-offs on the coach side. Unless the mystery wires is on the chassis side, there is no advantage to spent time on it, since this is not what you really want to preserve to make it match other 1974 rigs for legacy seek.