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Wires crossed on taillights: 1976 B300 motor home

5973 Views 4 Replies 5 Participants Last post by  MoparNorm
My '76 Class "C" Winnebago (Dodge MBH 300 chassis) has developed a goofball problem that has me pulling my hair: when I turn on the lights, they all work except the tail and license-plate lights. Turn signal and hazard flashers OK. Likewise for brake lights. Backup lights...well, when the automatic tranny is in reverse, the tail lamps (not lic. plate light) come on. However, pulling the headlight switch while in reverse turns those cross-wired tail lights OFF!

Oddly enough, the first time I drove this Winnie home, the lights were all A-OK. Somewhere along the line this problem appeared, probably during or after the last round trip (2011). I have a Haynes manual that covers the B-series vans; the chassis wiring for the MBH300 chop-van is the same. Everything I've checked thus far (terminals, plug-ins, etc.) matches what it's supposed to be. Aargh! Nowhere in the wiring diagrams does it appear that the main light switch crosses, circuits...with the back-ups, either (not that I'd expect such a thing).

I did remove and replace the battery before this happened and did discover a place along the undercarriage where a bundle of wires got pulled down by a curious raccoon (yes, raccoon: its paw prints are in dried mud beneath the rig). Can't find any broken connections.

Anyone have a similar problem. Meanwhile I'm still looking. I am certain that the wiring problem is in the cab/chassis, not the camper body.
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1,333 Posts
Sounds to me like some wire harness bundle melted together and you're getting weird shorting.

Additionally, I've heard of some vehicles where the right combination of fuses pop and weird things like this happen.

There can also be weird problems if body grounds go bad.

· Registered
3 Posts
Thank you for your input. I looked more closely to some of the wiring. There were several places that were covered up with electrical tape. I unwrapped two of those places and there was evidence of melted wires at several points they were melted together (the Insulation). I also noticed that House Wiring was used to replace some of the wires.

I want to replace the harness. Where do I go to Purchase one ? Also where can I find a wire Diagram ? Would Chilton or Haynes be a source ?

Again thank you for your replies!

· Active Jeeper
14,401 Posts
A harness for that year is going to be VERY hard to find. Sites that specialize in new old stock, like Brad's NOS, may have something, but you might be better off simply replacing the damaged wires one by one, soldering the connections and enclosing them with a new flex loom cover with shrink wrap on each end.
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