Damn, 2020 is not going down without a fight.

[Dr. Zoidberg]

I guess I've got a short somewhere in the longbed, perhaps. Blew an army of fuses today on the same slot that controls interior and exterior lights -- does anyone really NEED to see their gauges OR be seen at night? Overrated!

Checked my dimmer switch bypass. Rewrapped nicely it and confirmed power and ground. Didn't stop subsequent blown bois. My BIL told me start chasing wires. As if I know what the fuck I'm doing, but maybe I'll get lucky.

I love this truck, but man... It's had quite a few problems this year... will be 41 years old next month... Spending more and more time plugging holes than actually driving...

[Chariotoflove]

@dr-zoidberg If you need to see your speed gauge on the longbed, you’re probably driving it too fast anyway.

[jminer]

Oof - chasing shorts is always unpleasant work. You’re BIL is probably right, start inspecting wires for any worn insulation or bad connections.

[MM54]

If multiple fuses are going out at once, I'd check first with seeing what, if anything, is in common for those fuses, routing-wise (e.g. are all these circuits going through some particular grommet somewhere?)

[VincentMalamute]

@Dr-Zoidberg ah, I remember your fondness for electric circuits. Install a new wiring harness. How many wires could that truck have? It doesn't have 50 computers, CAN, LIN, and a few other buses, you have no excuse

[sdwarf36]

Is that a Datsun? Look at your battery. does the pos post have a cover? Is there any signs of it hitting the hood? I had a couple pick ups-had it happen.

[gettingoldercarguy]

@dr-zoidberg wanna rewire sometime? https://www.milspecwiring.com/

[Dr. Zoidberg]

@mm54 nonono, it's the same slot, one at a time

[pip bip]

@dr-zoidberg time to trade it in and buy a new ute/truck

[awesomeaustinv]

Pfft, seeing gauges is what flashlights, teeth, and/or duct tape are for!

[SilentbutnotreallyDeadly]

@dr-zoidberg

[RallyDarkstrike]

@sdwarf36 It's an old Toyota long-bed

[Old Busted Hotness]

Oh goody, "a short somewhere." That's always fun.

Start by determining the condition that blows fuses. Running lights only, or headlights? Start looking at places there the harness passes thru metal, like the firewall, or passes near metal like the headlight/taillight plugs. Could be a sidemarker, too. Does your truck have an illuminated ashtray?

The process is complicated by the fact that all the lights run off the same circuit, so the old "pull a bulb and see if the hot line is grounded" test won't tell you much. The blown fuse tells you that. If you're lucky it's in the headlight circuit; there's a lot less of that to check.

[MM54]

@dr-zoidberg said in Damn, 2020 is not going down without a fight.:

@mm54 nonono, it's the same slot, one at a time

You're dedicated, going through that many fuses

I would check to see what all is fed from that fuse, and disconnect as much as possible. If it still blows, you've eliminated a lot of the circuit from the possible causes. If it doesn't, then start reconnecting things one at a time - when one of them pops the fuse, you know the issue is in that leg of the circuit.

[Dr. Zoidberg]

@mm54 I'm worried there may be a problem with the switch on the stalk on the steering column potentially? Because if something is wrong with that, then all the other chasing I would do would be pointless. And I can test the circuit without turning on the lights...

[MM54]

@dr-zoidberg Are you able to disconnect the suspect switch and put in a new fuse? If it doesn't blow with the switch in-circuit, and does with the switch connected, it's either the switch itself or something the switch controls.

Do you have a wiring diagram you can share?

[Dr. Zoidberg]

@mm54

[MM54]

@dr-zoidberg Which fuse is blowing, from your description I'm guessing in the second picture the "TAIL 15A" ?

[Dr. Zoidberg]

@mm54 you are CORRECT

[MM54]

@dr-zoidberg Okay cool, that's a pretty simple circuit.

"Light Control Switch" has two "inputs" and one "output" - the "inputs" are on top/left, and when you turn the lights on, it connects them to the "out" (white/black) to ground. This then turns on the "Tail Light Control Relay" and the "Head Light Control Relay" which sends power to the tail and head lights, respectively.

The "TAIL" fuse should only be providing power to the lower-right row of bulbs, which narrows things down a bit. For starters (sorry if you already answered some of this above)

1. Does the fuse blow with the lights turned off?
2. Does the fuse blow with the "Tail Light Control Relay" removed?

[Dr. Zoidberg]

1. No, the fuse only blows when I turn my lights on.

2. I've not yet tested that

[MM54]

@dr-zoidberg That's a good sign for #1.

With #2, if removing the "tail light control" relay and turning the lights on blows the fuse, it's ghosts or something wrong in the socket / relay coil wiring (unless I've missed something). If removing that relay allows you to turn on the lights without blowing the fuse (the tails won't come on) then the issue is either in the circuit highlighted below or the relay itself.

To see if it's the relay, you could install a jumper from the +12v (R/Y) to the output (G) if you can determine the pinout for the relay, this would bypass having the relay coil in circuit but allow you to send power to the rear lights. If that blows the fuse (or melts the jumper, don't burn your fingers, it may get hot), the issue is in the wiring highlighted; if it works fine (you won't be able to turn them off like this) then it'd be the relay.

Unfortunately this diagram doesn't show connectors, which is pretty handy to locate a potential short circuit in that length of wiring.

[Dr. Zoidberg]

@mm54 Thanks, I will check out that relay as soon as I get more motivation. I just spent 3+ praying for a giant meteor while working on my wife's car.