Chinook RV

A friend bought a 93 premier on the ford e350 chassis, has no rear tail lights when the headlights are turned on, no roof perimeter lights, the brake lights flash when the turn signals are used and turns off the cruise control off every time you use the turn signals. replaced a faulty ignition lock and switch, combination switch and cant find the ford factory electrical trouble shooting manual for the model year to correct the problem so this thing will pass inspection . i have power to all the fuses in the factory fuse box or power distribution boxes. found no other fuse locations that might have been added to power tail lights . and it looks like some mook wired it to trailer lights instead of the factory chassis lighting . i disconnected all the lights and trailer hook up, probed the wires that ran uder the left chassis and same probelm is still there. front markers and turn signals work fine. any help would be greatly appriciated considering nobody will touch one thats this old with this kind of problem .

if I followed your words correctly.. it's a fairly common problem (unfortunetly). If sitting in the driver's seat, to the left of the steering wheel and up under the dash.. theres a fuse box (maybe a second bank? not the ford orginal? I'm not sure). to the top right of that box theres a wire that gets pinched and pulled out ever so slightly. if you wiggle the box around while looking up at the 1 yellow running light (if its dark enough outside to see).. eventually it should flicker on.
the long term fix varies some.. but theres the problem.

Howdy,

To basically repeat what Manitou said (and if a 93 is the same as later 90's and beyond) a contributing factor might be that Chinook used the electrical line that Ford put in for the trailer connector for the taillights and marker lights (but not the headlights). I have written more about it elsewhere, with diagrams (might come up in a search), but the gist of it is that Ford has two wiring runs that end in little "schnozzles" back in the driver's side frame rail at the rear. The brown one is the common four trailer wires (the back one is the other, less common trailer wires).

So Chinook used the brown one for the 4-way flat trailer connector, as per Ford. BUT, they also took those four wires and brought them up through the floor and used them for the taillights. And the marker lights (even in front). However, they wanted a fuse. So they ran the wire all the way forward (to the auxilliary fuse block by driver left ankle), then ALL the way back (goes through under plastic footwell cover in cab then along frame). So if you ever tow a trailer with a number of incandescent lights, there goes your fuse and your taillights and marker lights (easily solved nowadays by going to LED trailer lights).

They also took one wire from the black schnozzle for the backup lights. Not sure if that one goes forward and back, but anyway same concept.

Could be a connection, but the fuse is an easy one and often the culprit (skinny wire = small fuse) (long skinny wire + more lights = lots of voltage drop = higher amp draw = blown fuse).

I had no problem towing my boat trailer with LED lights. Then I hooked up a cargo trailer that had like 28 incandescent lights. There went my tail and marker lights (on the road, natch - it was fine when I first hooked up). I was going to replace them with LED lights anyway, so did that and no more problem (much less load with LED lights) after I replaced the fuse (it's 7.5 amp as I remember it).

So to recap:

1) Ford provides two trailer connector schnozzles in the driver frame rail right at the rear (you are supposed to connect these to Ford pigtails, hence the snorkel connectors).

2) Chinook also used these to power their taillights and marker lights.

3) They used long, long, skinny wires.

4) Trailer lights (if many and incandescent) can be too much amperage.

5) Fuse that is in Chinook added fuse block by driver left ankle can blow (labeled "marker lights").

6) Wire runs forward along driver frame rail in black ribbed loom, through under driver's plastic stepwell cover, to fuse block area, then back again (plus up to marker lights on overcab).

The crimps are just the old fashioned relatively crappy type, so one of those could have failed as well. Fuse is most likely though.