so I'm driving home last night and notice none of my rear lights are working...No tail lights, turn signals, tag lights...nadda. I get up today thinking it was a fuse, nope. Followed the harness, everything seems intact. So now I'm at a loss. What would cause such a sudden loss? DO these things have a fusible link someplace?

No FL, have you checked the Headlight switch?

Everything up front works....

Marker lights too? Maybe some rogue squirrel chewed through the main harness to the rear? If not, I'm stumped.

yeah nothing outback works.... i'll have to get the volt meter I guess and start testing and see where the power stops.

The year of the truck would be helpful. Lots of wiring changed through the years for rear end lighting.

If everything was lost suddenly, there is one, and possibly 2 grounds at the back of the truck that all the taillights/brake/turn & license plate lights use. I'd start looking for a bad ground. The 70s trucks grounded the tail lights through the screws that hold the light fixture to the body. A bit of rust on the screws, or the sheet metal the \screws go through means poor lighting. By the mid 80s, Dodge added 1 ground wire foe the entire rear lighting, then a few years later, added a second ground. the 2000+ trucks have several grounds, and may also have the lighting ran through a lighting computer. Good luck with those.

I usually grind a clean place at an easily accessible location on the frame (grind clean both surfaces of the frame at that location), then I will drill a 1/4" hole through the frame and install a 1/4" x 1" long bolt with flat washers on both sides, and a nut and tighten the bolt to the frame. Then I will add a specific ground for each light and connect them to the bolt with 1/4" eyelets. Then add a second nut to secure all the wire eyelets to that bolt. 4-5 years later, then everything starts getting crusty, just reclean the frame and replace the bolt and whatever eyelets need to be replaced.

The next question is, does the fuel gauge still work? Gene

sorry 91 W150. The factory harness has been cut into. Somebody wired in MSD, it is now carb'd. The big ECM has been removed. My dad said he had the same issues w/ a 88 RC. It was the light switch. Everything goes thru that I'm guessing. When the ground dries up I'll go look for at the grounds.

A 91 still has the old fashioned lighting system, it wasn't until after 2000 sometime when the lighting computers came along.

As a side note, if someone cobbled in a trailer hitch plug connection to your truck, I would start by checking out the wiring for that trailer hitch plug. those trailer hitch plugs are often the cause of tail light problems. Those quick connect blue things most use to connect the hitch plug to the truck often break or badly corrode the truck harness wires.

The tail light (and plate light) function comes off of the headlight switch, both tail lights come off the same wire terminal on the headlight switch. That wire generally travels along the frame to the splice where it splits, one wire enters the left tail light 4 wire terminal, the other side of the split travels across the rear frame crossmember where it again splits, with 2 wires leaving the splice to go to the license plate lights (a right and a left light), and the main wire continues to the right side tail light pig tail.

A 91 should have the specific ground spade on each bulb socket in the tail lights that would connect to a single terminal in the square taillight plug on the light side. I believe all the grounds on the frame side are still grounded to a single contact point on the frame, but I don't remember where that is.

The square pigtail plugs tend to have a few issues. They have 3 female terminals and one male terminal on the frame side and 3 male and one female on the light side. for each side of the truck. The odd terminal is the tail light ground terminal. One of the three of the like terminals would be the tail light terminal, one terminal would be turn/brake, and the 3rd terminal would be for the backup light. It is not unusual for any number of those male terminal posts to corrode and break off.

The stop/rear turn light power travels through the stop light switch at the brake pedal, then that power goes into the turn signal switch. Its at the turn switch where the brake light is separated from the rear turn. Each of the 4 turn signal power wires has its own power source from the turn signal switch. One power for each front turn signal (the dash indicator lights are powered through both front turn lights), and one powered for each rear turn signal.

I think on your 91, after checking the hitch plug connection, I would start the the search for the issue by looking at each tail light square plug. pull the plug apart and inspect the condition of all the terminal ends. It that is good, you can test the ground to a good ground source with a continuity tester. With a test light you can see if you have light power at those terminals too. Gene