Melted Wiring Harness (1 Viewer)

[45Dougal]

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

Any idea how much current those old alternators can pump out?

 

[ToyotaMatt]

Any idea how much current those old alternators can pump out?

that AMPS Spec. on a 1976 FJ40 2F Alternator can vary from 45-50-55 AMPS depending if it was fitted with a Cold Climate Spec. SNOW VERSION 55A
unit or only the base 45A units that were on all Gulf State Region ones ....

all Land Cruiser alternators have the raw DENSO's in them if un-regulated to do what has occurred to your truck

 

[45Dougal]

that AMPS Spec. on a 1976 FJ40 2F Alternator can vary from 45-50-55 AMPS depending if it was fitted with a Cold Climate Spec. SNOW VERSION 55A
unit or only the base 45A units that were on all Gulf State Region ones ....

all Land Cruiser alternators have the raw DENSO's in them if un-regulated to do what has occurred to your truck

Not my op, just curious.
Certainly enough to sauté those cables if they were shorted at the fuse box, although I wouldn't expect anything out of the alternator if the field wires were disconnected.

 

[ryanwk628]

I grounded out my harness. Pulling it was actually easier than trying to work under the dash, and I could rewrap it all before putting it back. I also addressed some worn and corroded terminals and used good 3X heat shrink in places that never had. I ordered the correct colored wires to keep the chart correct.

I made sure to check for continuity on all circuits just to make sure nothing else was having an issue. I also checked to make sure there was not continuity across adjacent circuits that passed near the area that got hot. @Coolerman had all the bits I needed

 

[fjwagon]

Doing continuity checks was brought earlier. If it's broken connection that helps with locating the culprit. However, if you have a cold solder joints(s) it msy still pass a continuity test but will fail on a load. And I believe there are solder joints in that wire harness. And If you are convinced the harness is an issue maybe stripping back and check the solder joints and resolder them if they are indeed bad. I hope thus helps.

If you have solder use solder Flux your connection and solder. Use isopropyl alcohol paper towel and acid brush to remove the Flux. I prefer dipping the acid brush in alcohol and brush it on the solder joint back forth until it looks clean. And put the paper towel on top to soak up the resin. May have to repeat. Easy peavey.