sbagdon

Came home last night to the oddest thing... pull up, and the parked '92 Pickup had it's marker lights on. Dug into it, the tail circuit was energized... front markers, rear tails, and dash were all lit. Playing with the headlight switch didn't turn off the markers/tail/dash (yet did what it was su pposed to do with the headlights). Pulling the tail-fuse would turn the lights out. Unplugging the steering column plugs didn't turn off the markers (there's three plugs, ignition, lights, wipers... did I miss one?!). No recent electrical or wiring work, situation just popped up.

All research indicates that it's a bad "combo" (headlight) switch, yet confused, as appearing to unplug the headlight switch didn't turn off the tail circuit.

Can't find a tail relay, no problem finding the healight relay. Is there a tail relay?

Digging through Google to find a body-harness diagram, yet anyone know what would energize the tail circuit, even when the headlight switch appears to be unplugged?

Anyone know if there's a jpg/gif/pdf of the '92 Pickup body harness diagram floating around?

Thanks!

Gamma_Hugo

does it happen when you press the brakes? a similar thing happened to me but it only happened with the brakes, in addition when i would turn on the headlights, the brake lights would stay on as if i were pressing on the brakes and would stay on. it turned out to be a bad bulb from the rear light assembly. I solved it by having someone press on the brakes and pulling out the bulbs one by one until the dash and the markers stop lighting up when it was pressed.

scope103

If unplugging the combination switch does not turn off the taillights, your taillight relay may have failed closed. http://www.ncttora.com/fsm/1990-1995...e/headligh.pdf The relay is located in the driver's side kick panel. http://www.ncttora.com/fsm/1990-1995...e/powersou.pdf (the exact location of all these relays is very model dependent, so the picture probably won't match. Use your head.)

Pin 2 and 4 of the relay are both connected to 12v. Pin 3 goes on to the tail light fuse.

While you have lots of opportunities for bad wiring, I'd start by pulling the relay. If the taillights go out, you're almost home.

sbagdon

Nope, for me, this isn't a brake/tail circuit short. Yet for you, this makes a lot of sense, in that if the dual-filament bulb (3157?) were to bridge, it would back-feed between the brake circuit and tail circuit. Yet it would also appear to mean that if you clicked the headlight to the first position... the brake light circuit would be energized...

And that makes sense. The headlight relay is easy enough to find (Relay Block 2, with a labeled lid), and functions normally (switch position, and removal). I figured there was a tail relay, and was heading there next, yet wasn't sure where it would be, as the fuse cover only displays fuses, not relays (and don't have a harness diagram yet) . BE-11 Juction Block 1 shows me where the Taillight Control Relay should be, and I remember it from last night, so I know what to head to, to pull-to-test. Thanks you for one huge bread crumb!

I'm inclined not to believe it's bad wiring, as there's been almost no change to the Pickup in a while. This was a sudden event, so I'm more inclined to believe it's a relay, not a switch or wire. I'll update after more debugging.

Yet for humor, just to show you how un-optioned my Pickup is... Junction Box No 1 in BE 11 and in my owner's manual both show a sub-block, for fuses 10/11/12/13. Yet for this Pickup, that would be for power steering, speed controls, and rear anti-lock brake. I have none of those (yes, a Pickup without power steering, thank heaven's it's not a V6!), so they didn't even bother installing the sub-harness. It's sometimes frustrating when the manuals show something, and it isn't in your vehicle. The sub-block just isn't there. It is one simple vehicle.

sbagdon

Yup, seems it was the tail relay. Checked the Pickup after work, put the fuse in, and lights were out. Flicked the light switch, and the lights flipped on/off, and I could hear the tail relay clicking. It wasn't clicking yesterday, so... it must have gotten stuck in the "on" position. One thing to note is that it was very humid today, mostly from rain. Will check a few more times, for lights and relay-clicks, yet appears the tail relay was the culprit.