Melted Wiring Harness (2 Viewers)

[cooksflips]

Hey Everyone,
I would really like some help with this one. 1976 fj40 with factory 2f and wiring harness. I neglected to plug in the two small wires connecting to the alternator (white with black and white with green) and i went for a ride and almost smoked my hole harness. So far from what I can find this resulted in melting the large white wire and white wire with blue line which run from alternator to altmeter and then back to battery where i do not have a fusible link. Immediately after this happened I could still crank the truck. Also the left blinker light in the gauge was staying lit. I have replaced the melted wires and gone through the harness and can not find any more damage. Now i can not get any power to the fuse panel.
All fuses are good. All grounds are good. No fusible link in harness. Where am I losing power ?
I can not get any power at the barrel plug either? This is the factory harness that has just been worked on for years. maybe time for a new harness.
- John

 

[JackA]

More info on your truck would be useful. What year, motor, mods, etc?

 

[cooksflips]

More info on your truck would be useful. What year, motor, mods, etc?

it is 1976 fj40 factory 2f with original wiring harness

 

[pjohnson]

Did you pull the harness out to inspect and repair?

That's about the only way to be certain you fixed everything. Also, plugs can melt inside and cause issues that may not be readily visible

 

[thorslc1977]

No matter what you find is the problem after all that work a fusible link would be a good Idea. @Coolerman has a very inexpensive fusible link set up for your '76

 

[pb4ugo]

Did you pull the harness out to inspect and repair?

That's about the only way to be certain you fixed everything. Also, plugs can melt inside and cause issues that may not be readily visible

^^^^^^^THIS^^^^^^^

Usually, when this happens the damage occurs deep in the harness. Any adjacent wires next to the white/Blue wire & white wire get burnt too. You need pull the harness to strip back all the tape and inspect.

 

[45Dougal]

Sounds painful, nobody wants to smoke their hole harness.
Seriously though, I don't see any obvious failure mode where that should happen as a result of not plugging in the regulator wire - is it possible that the white-blue wire shorted to the alternator housing if you've been working down there?
That could have burnt out your ammeter shunt. Check for volts on the ammeter.
If its dead then short it out for a temporary fix with a good thick wire.

 

[cooksflips]

Did you pull the harness out to inspect and repair?

That's about the only way to be certain you fixed everything. Also, plugs can melt inside and cause issues that may not be readily visible

I did not remove the harness but I did expose much of the harness in the dash to the point that I feel very good about not having damaged any other wires. The melting of plugs is something im not sure about. I have not seen one melted yet.

 

[cooksflips]

No matter what you find is the problem after all that work a fusible link would be a good Idea. @Coolerman has a very inexpensive fusible link set up for your '76

Yes certainly.

 

[cooksflips]

Sounds painful, nobody wants to smoke their hole harness.
Seriously though, I don't see any obvious failure mode where that should happen as a result of not plugging in the regulator wire - is it possible that the white-blue wire shorted to the alternator housing if you've been working down there?
That could have burnt out your ammeter shunt. Check for volts on the ammeter.
If its dead then short it out for a temporary fix with a good thick wire.

it is possible the white-blue shorted to the alternator housing. I have volts passing through the ammeter to the wire running back to the alternator so i would think my ammeter would be ok. What i cant figure since I have current passing through the ammeter is why I then would not have power at the fuse box ?

 

[45Dougal]

it is possible the white-blue shorted to the alternator housing. I have volts passing through the ammeter to the wire running back to the alternator so i would think my ammeter would be ok. What i cant figure since I have current passing through the ammeter is why I then would not have power at the fuse box ?

Do you have power at the ignition switch socket? Same wire.

 

[pjohnson]

We'll, if you don't have one already, this should help...

Cruiser Wiring

 

[cooksflips]

It is my understanding the positive wire from battery running to the ammeter gauge also powers the the gauge panel and this is where the barrel plug gets its power ? Then sending power to the fuse box. If power is passing through the ammeter gauge then why is the barrel plug not receiving power ? This is my current dilemma I believe ...

 

[ToyotaMatt]

it is possible the white-blue shorted to the alternator housing. I have volts passing through the ammeter to the wire running back to the alternator so i would think my ammeter would be ok. What i cant figure since I have current passing through the ammeter is why I then would not have power at the fuse box ?

by having the 2 large 10ga gauge wires white w/ blue tracer stripe and solid white pulled off the back side of your gall tube fuse box at the same time ...

- and actually starting the engine , then taking her for a spin , when 2F engine RPM's increase to a minimum of lets just say ...

- 2700-3300 RPM's on average low side of my chart here ...

- the moment that Alternator begins to rotate from the drive belt , it's in a FULL FIELD or FULL FIELDING state of being ....

- FULL FIELD is when a alternator can exercise it ability to produce the the most possible AMPS it can achieve in the conditions of being un-regulated , buy the Voltage Regulator on your fire wall ......


- this extremely remote possibility of ever occurring in the first place is the sole stand alone reason why when still under a TOYOTA Factory 3/36 bumper to bumper warranty that was exactly the same back in 1976 till the last possible Remotely Mounted Voltage Regulator equipped TOYOTA vehicle platform USA spec. rolled off at LONG BEACH warf and its Keys found there way into some ones pocket or purse DOFU ....

or Date of First use ...

- always the dealers parts Dept. would automatically add and or order up a new 27700- with any Alternator has Failed covered Warranty under the 3/36 time window ...


- i always offer any 27020- NON-Regulator equipped NOS alternator with a mandatory 27700- or as i to call it a Alternator KIT ...

- because i would never even think for a metric second to install one on my personal TOYOTA vehicles without doing just that ..


NOTE : i will report back shortly with the concrete verifiable tech. of what exactly was the last USA Spec. Toyota to actually have a remotely mounted 27700- type external voltage regulator ?


- forgetting the milestone threshold in all things TEq is nothing less then a professional failure for me

 

[45Dougal]

Maybe you just replaced the yellow bit but not the pink bit?

 

[MOTOV8R]

If you aren’t getting power anywhere looks like you need to trace the white wire. It does run through the ammeter and then it’s blue/white. I would also check for continuity for these wires to ground as you are troubleshooting. It’s more likely that it shorted somewhere to ground than that it created a complete open in the circuit.

http://www.globalsoftware-inc.com/coolerman/fj40/schematics/FJ40/1976FJ40/1976_Toyota_LC_FJ40.pdf

 

[cooksflips]

Do you have power at the ignition switch socket? Same wire.

I do not. But when this initially happened the engine would crank and run it was just not charging with the alternator.

 

[cooksflips]

Do you have power at the ignition switch socket? Same wire.

I do not.

 

[cooksflips]

View attachment 3283969
Maybe you just replaced the yellow bit but not the pink bit?

I think this could be the issue. I did not know the wire split. Using an iPhone now and these images are difficult to see. Will be back on it in the am.

 

[ToyotaMatt]

I think this could be the issue. I did not know the wire split. Using an iPhone now and these images are difficult to see. Will be back on it in the am.

you should consider it a needed step now to remove your alternator from the engine , and take it to a known & reputable repair shop , or like a NAPA or even ADVANCE auto parts , that indeed has a full wide range functions manual belt driven testing machine , to confirm and verify your 27020- is in good working order after the thread title topic above occurred ...

- generally if a NipponDenso OEM TOYOTA 27020- full-fields for any reason , the life-span of one or more of the diodes on its rectifier board cease to exist instantly ...


- the remote but real possibility you suggest above , the 2 white wires that are on the back side of the fuse box , one with a blue stripe , suddenly touching together as you were driving is a real possibility ...

- what is also a more likely possible scenario here i think for sure is , one or both found a direct path to Negative N- Ground via any possible metal like a 10mm hex bolt MALE threads that affix the glass tube fuse box to to the kick panel protruding out past the captured spot welded female nut

- you should look for evidence of both the above , that will lead you to the focus point of damage that created the smoke you experienced if present ?

- lastly , have you by chance examined in good detail , the GREEN 4 pic connector plug and its HARNESS side mating buddy , from the column mounted key switch down ?

- when something like this occurs , that exact location between the green connectors , can and does often have a little melt down of its own inside between the brass male and female terminals , that can;t actually be seen if you do not try to physically un-plug the 2 apart ...

- this is one reason why you see all the CHINESE made clone FJ40 green plug electric key switches for sale everywhere you go online these days popping in your face on AMAZON for example ..

..
hope this helps

good luck