Yodes

Just had my 1991 v6 truck start blowing the dash fuse. Replaced it and it blew right away. Its an automatic after the fuse blows in order to move the shift lever i have to use the shift lock override button. No gaues except speedo and no dash light Other than that the truck runs fine. The first fuse that blew and came with the truck was a 15 amp fuse even tho it calls for a 10. Is that ok? Should i replace with a 15 and see what happens? Thanks

old87yota

If the fuse blew right away, you most likely have a direct short somewhere in the circuit.

You will want a wiring diagram of everything that runs off of that fuse. I am not very knowledgeable in finding shorts but I do know to never install a bigger fuse. ALWAYS use the fuse that was specified. If a fuse blows at the specified rating, something is WRONG. A fuse is the circuit protection device to prevent the wiring from burning up in the event something goes wrong.

This is why you shouldn't install a bigger fuse:


Others who have found short circuits before can help you way more than I can.

scope103

Just what do you think would happen? Let me give you a hint:


The good news: you don't have a "Dash" fuse. Feel free to just leave it as is.
I'm going to guess you're blowing the Gauge fuse. http://web.archive.org/web/201204170.../2powersou.pdf In addition to the, uh, gauges, it drives the back-up lights, the heater, antenna, Light reminder, Door locks, cruise control, ADD, CEL, and a bunch of other stuff you really need.

So, obviously, you have a short somewhere. But where? You've given us a clue: the prior owner put in an over-sized fuse. Why? I'll bet he's hooked up something (radio, amplifier, gps, ...) to the gauge circuit and overloaded it. For a while. But now that expert (?) wiring has failed completely and shorted.

So I would look for anything under the dash that doesn't look like it was installed in Tokyo. That's where I would start looking for the short.

Just to help you along (a box of fuses will get expensive after a while), you could consider temporarily using this: https://www.harborfreight.com/30-amp...ter-67724.html

Yodes

Ya my bad i ment gauge fuse. Thanks for the info there is some old speaker wire rigged up from the P.O ill rip up some more panels and check it out tomorrow. Also found some wires going to the trailer hitch that were rubbing on the frame to dark to investigate farther.

wyoming9

iTrader: (1)

Quite possible the back up light switch shorted or the wires rubbed through that happens quite often

Increasing the fuse size is not really a good idea .

Truck starts on fire attached garage is burning the fire company did save the foundation of the house that was not my best day

Yodes

It seems to be blowing the fuse as soon as i put the truck in reverse and stays fine until that moment.
Back up light switch is that something under the dash or under the rear of the truck by the light itself? Either way ill figure it out tomorrow . i have most of the dash off couldnt find any shorts yet. The amp and speaker wires left by the p.o though done very half assed and not going anywhere were intact after cleaning them up tried a new fuse with no luck. Im shure that must run off a diferent fuse any way. The wires have been there for 2 years since i got the truck with no issues of course my stereo never did work. Checked trailer wires where they were rubbing and the wire casing seemed intact just the tape had rubbed off. Having some trouble removing my non working stereo im going to remove the rest of the dash and get in there hopfully instal my old amp and stereo while looking for shorts

wyoming9

iTrader: (1)

Your back up light switch is on the transmission .

Without looking I can`t remember what side.

I don`t know why people start pulling the dash apart it seems like the first thing some do .

Check the easy stuff first .

Yodes

Passenger it seems. I did check around my trailer and reverse wires first i needed the dash off to check p.os jankey stereo wires anyway and ill finaly get my old stero installed in the prosses.
After finding out it blows in reverse i did some more research and i have a few things to check mainly that switch

scope103

Here's the pin-out of (the most typical) Park-Neutral switch. http://web.archive.org/web/201408160...37parkneut.pdf

Before I messed with the switch, I'd examine the tail light assemblies, only because they are more exposed to abuse. (And sketchy attempts to install trailer wiring.) You should be able to remove the taillight assembles and unplug them. If you blow a fuse with the assemblies unplugged, then move onto the switch.

SInce you have an electrical problem, you need a multimeter to look for it. (Those electrons are just too darned small to see!) I assume you have one. If not, no excuse for that: https://www.harborfreight.com/7-func...ter-90899.html

RAD4Runner

Yes. Poor wire management on first-gen shown here: https://www.yotatech.com/forums/f199...l#post52023759


YES! Next to our senses, the multi-meter is the most important troubleshooting tool.

Yodes

back up light switch centre right fitting? being shorted by my leaking rad fluid/ engine oil? the cable to it goes to the black connector you can see
Back Up light Switch? lower of the 2 bolts on side of trans
Park Nuetrel Switch.. Theres also something almost identicle to this on the oposite (Drivers) side except with a smaller push rod

This is the connector going to the possible reverse light switch in second pic. it has 2 wires

let me know if i have this right theres a couple different wires coming off the transmission and i cant find my exact model transmission in any diagrams. and i was planning to put some wire inbetween the connector to complete the curcit to test reverse light switch. if it comes on with the key turned i have a bad switch. so i want to get it right and not mess with the wrong thing.

Yodes

P.O split this red wire on the left tail light and grounded it on the frame. why i dont know but never caused me a problem before. could this now be ˟˟˟˟ing up? lots of connections are just taped together no sodder or crimp ons or anyhtin mainly just stereo wires. the kid that sold it to me had his dad who owned an electrician company helping him with electrical work i dont know how it ended up like this..

I recently got a multi-meter still learning how to use but continuity is easy as long as i can get to the right wires inside the clusters and probe them properly wich on the top of the trans is pretty hard

scope103

The back-up light should be R-B (Red with Black stripe), so if that's grounded it SHOULD blow the dash fuse as soon as you shift to reverse.

Funny thing, though. The PO didn't "ground it to the frame," he connected it to the truck bed. On my truck, the truck bed is NOT at ground. (The frame is, but the bed is mounted with rubber vibration insulators, which means there is not a good electrical connection bed-frame. Which is WHY there is a separate wire (W-B) to provide ground to the taillight assembly; you can't count on grounding it to the body.)

I suppose that the bed connection just didn't do anything for a long time, and after a few years of vibration you got an intermittent connection to ground through the body. (It is held with steel bolts.) It wouldn't surprise me at all if removing that bed connection clears up your problem.

But that doesn't answer WHY the PO did that. One possibility is a broken ground wire (W-B), coupled with a broken reverse switch. By shorting the backup light to ground, the taillights would work (sorta) as long as the reverse wire (R-B) was never connected to 12v. Maybe your reverse switch has intermittently started working again.

So now you have a good project to learn multimeter work! Good luck!

RAD4Runner

Yikes! Better warn the NEC and the fire department about that guy's projects! LOL!
Yes, like Scope says^^^ ground on classic Toyota's is typically white wire with black stripe.

Yodes

Thanks that helps ill try taking off that bed ground and see what happens as well as try to track down the original ground wire.
Can anyone help identify my reverse switch from the pics? Or provide a proper schematic. Im sure its one of those two bolts but cant find any scematics that pin point the location for my truck. Similar transmissions have a large easily identified and accesable switch near the bottom of the trans on the passenger side mine is not so straight forward. And my manual doesnt help at all

scope103

Your "reverse switch" is part of the park-neutral switch. I don't know exactly which transmission you have (it's listed on the door pillar), but you almost certainly have the wire to the PN switch, a bundle of solenoid wires, a temp sensor, and a speed sensor. The PN switch is probably a 10 position connector, but I don't which transmission you have (and I don't know all transmissions).

BUT, so far you've identified a mis-wiring that is very likely the cause of your problem. If it were me, I'd work from the taillight to see what I can eliminate. Start by removing that bogus "ground," and disconnecting the connector from the light assembly. Then check for continuity to ground on W-B (if that's broken you'll have really weird gremlins), and look for switched 12v on R-B. Only if you don't find switched 12v on R-B do you need to look at the PN switch.

Let us know.

Yodes

Oh ok so the park nuetral switch is what i have to check. On you tube theres a guy with 1993 toyota and it seems his is seperate and a breaze to remove. A/TM g253 i assume thats the transmission type on the door frame. I took off the bogus ground and now my problem is gone it seems. Put in a new fuse and its holding all my lights work fine. For the continuity test for the ground i have to find where it grounds on the frame and test between that and the light? The wires kinda just disapear into the frame rail from what i can see.
Got my new stereo installed working great >

scope103

If all the lights (reverse, turn, and parking) work, then your ground is almost certainly fine. (The problem is when the ground opens, and one light grounds THROUGH another. So both light weakly.)

That just leaves the mystery of WTF was going on?

Yodes

The truck still works fine bit of a mystery indeed. I remember when i first got the truck one of my turn lights or running lights was not working. That funky ground wire the p.o put in had slipped off where it was bolted on and tightened it back up and everything was fine. now removing it fixed my fuse problem and everything else still works..

RAD4Runner

The truck bed should be properly grounded. Ideally you would physically trace the wires to positively be sure that a ground wire runs to that corner with the tail lights. IF impossible for you to do so, ensure that the bed metal is properly grounded by:
1) Properly connecting a ground wire to the screw ground like below (next to the gas door opening knob),
2) Properly running it along with stock harness to the truck bed,
3) Properly connecting it to easily-accessible metal of the truck bed.

Proper electrical connection should have bare, shiny metal tightly contacting bare shiny metal. I strongly recommend doing it to the stock ground screw behind that driver side kick panel as well.