40 series hacky wiring — help I.D. ?

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swamp-thing

swamp-thing

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Hiya gang, I’m dealing with some hacky & nearly perished wiring on an 11/79 FJ40.
The truck is operational, so neither of these issues are showing signs of a serious problem (yet) but I want to button them up cleanly now before they do become an issue.

First pic shows the positive battery terminal where I have 2 wires that splice and disappear into the harness.
I’d love to know ( if anyone can I.D. ) what the two wires may be for….I suspect the OEM fusible link setup has been removed and something else put in ( maybe fusible…wire?? The yellow and blue junk —I dunno ) If so, What do I replace it with and then what is the other spliced wire for (red)?

The second picture shows a wire attached to an alternator post ( I have it flagged with green tape ) that is in such terrible shape, sheathing deteriorated and wires exposed with corrosion visible. Short of unraveling the whole loom, does anyone know where that wire is heading and if I can replace all start to finish, or do I need to splice in a repaired section…?

I know search is available, but it can be intimidating to an electrical dolt like myself, plus I like to hear from y’all and I know many of you are just cruising around Mud & love to help solve mysteries & share knowledge!!

Many thanks

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Your +pos (black with terminal) wire is may too small that's like #4 size and would work way better if it was red an 2/0 size.

You need a wiring diagram free

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I have the '79 and while I've used the toyota wiring diagram...I've started liking this one better that
coolerman hosts. There are multiple pages to this diagram hosted as different jpegs.
You are right in the zone of fusible link and wiring to your starter. I would DEFINITELY unwrap it back to the
firewall and look at everything at least in the engine bay. You're running but you can be in a hazardous
situation here.


I'm not recognizing that alternator. Most of the 79s I've seen have an internal regulator in the alternator ... but this
alternator has something on the top that I'm not familiar with. I tell you this because some of the wiring for the 1979s
have slightly different components depending on market.
 
cool ... that may be what the original oem looked like. The wiring diagram I was pointing you to shows a regulator separate from the alternator. I'd snake that white/blue wire out for sure and get a fusible link from coolerman. I think that white/blue wire of that gauge is going to only be in the engine harness part.
 
Yep, that melted wiring definitely needs some attention.

And I second that wiring diagram mentioned by Wimberosa. It really helped me when correcting my 79 wiring.

Focusing on that schematic, specifically regarding alternator-to-battery wiring, you should have a white with blue stripe wire (WL on the schematic) between the two and an inline fusible link (which has a lead on either side going to your 50a ammeter).

If anything is wrong in that area, melting can result. Lots of current there. My meter had been melted by the PO and no fusible link was in place. I think folks don't understand how it works.

A little background, the alternator pushes current through that line, which charges the battery. That current, going through the fusible link (which has a slight resistance), creates a slight voltage drop across that FL, which is detected by the ammeter, and moves the meter (also very slightly, if you're lucky).

I'd definitely make sure all of that is intact. @Coolerman can fix you up with that segment if needed. Then, maybe explore from there to verify your wiring matches the schematic. The color coding really helps.

Fyi, not sure what that red wire is doing, but you might include that in your discovery process. And a look at upping the gauge wire in your starting circuit if needed.
 
Thanks guys — yes for sure any crispy melted wire is a hard pass, so I will be fixing this post haste.
I’m actually looking at the hanes book ( one of a few random manuals I do have ) and it looks like possibly that melty alt wire might be linked to the s*** happening on the battery + side. This truck has been a 1 owner in the town I live so it’s seen its share of local rural colorado mechanicery and never been to a specialist, so it wouldn’t shock me if they did whatever it took to keep it on the road by deleting the fusible link…..

Appreciate y’all for the replies!!
 
Im not familiar with the 79 wiring, but thru the yrs Toyota used similar color codes on their wiring. The wire you tagged with green tape appears to be the white/blue stripe wire and is the wire which goes to the fuse box and the negative side of the ammeter. It's marked negative on the back of ammeter but is in fact hot+ and powers the vehicle from the alt side. It is an extremely important wire and is in bad shape. The melted insulation indicates the wiring had a pretty catastrophic event happen. Im surprised the harness still works. The bluish wire at the batt with the yellow butt connectors appears to be fusible link wire, but that's just a guess. If it is, it should connect to a heavy white wire and eventually go to the positive side of the ammeter. It's extremely important also and connects to the white/blue wire at the ammeter. Im guessing the red wire might have something to do with the alt smaller wires. Imo, the harness needs to be pulled, completely stripped down and repaired. The damage to the white/blue may have gone deep into the harness and compromised other wires, the same goes for the crispy wires on the positive side at the batt. The harness needs to be repaired correctly. There's no telling how deep the damage goes, without looking. Coolerman sells color correct wire, terminals and plugs, and he has wiring diagrams available.
 
You might disconnect the battery, pull the gauge cluster, take a look at the ammeter terminal ends. With the cluster pulled, check the continuity/resistance of the ammeter (-) wire. That could help you decide how F***ed you are.
You do not want to accidentally short-to-ground the ammeter wires, you'll fry the harness, which could be why you have the mess to begin with.
I bypassed the meter altogether. Cut/spliced/crimped/wrapped with electrical tape my ammeter wires together to avoid ever having an accident.
Get a new fusible link from @Coolerman
Also @Fourrunner sells robust battery cables, you may consider picking a set up.
 
Also not sure what that red wire is doing. It looks like it may be connected to the small W/L and B wires that go to that black plastic fuse box for the ammeter that is taped to the harness with yellow tape. I suspect the wiring you are looking at is this.

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I'm currently going through something similar on my August 1978 built 1978 FJ40. Despite my wiring being almost completely original (except instead of a crispy blue wire from the original battery cable, it's a severed red wire and instead of my WL wire from the alternator that goes to the ammeter being fried, it's my ground wire.), the wiring diagram is directionally correct, but sometimes colors are incorrect and splices aren't where you'd expect them to be.

Having said that, I unwrapped my harness as far as I could to see how far back the crispy wires went - I ultimately removed the entire harness to repair any and all damage.

That White w/ Blue stripe (WL) wire from your alternator is extremely important. As others have mentioned, at a minimum, I'd disconnect the battery, pull the gauge cluster, check the ammeter terminals, check the fuses to the ammeter (if accessible?), check the condition of the WL wire at your ignition switch and at the back of your fuse panel. Checking for resistance and/ or continuity like @samatulich said is important, but a visual inspection would be enough to send me down the rabbit hole. Cleaned up wiring + new fusible link will prevent future chaos.

​

 
I think your PO and my PO were brothers. I have almost the same horrible wiring I'm slowly going through, wire by wire, and fixing or replacing. I'm pretty sure my PO thought twisting 2 wires together and wrapping with electrical tape was a sufficient electrical connection.
Some of the hassle is just getting access to the wires wrapped together in the wire harness. I taped together a couple of the wiring diagrams from the factory manual and put them on a 36x24 sheet a paper. Found it was easier to trace the wires out on a big diagram vs flipping pages back and forth. This is for my 1977 but I would guess mostly apply to you.
 

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swamp-thing said:
Thanks All!

I'm sorry for show-and-tell but I'm starting to formulate the issues based on your comments, EWD, recommendations etc.
If you can follow my roadmap to success, does this look about right for what needs to be done?

TIA!

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Seems like a good plan! Very similar to what I faced with my 79.

A couple of notes:

- I ended up removing and correcting my entire harness, but you may not need to go that far. It might help to try and figure out what caused the melting and determine the extent of the damage by examining the endpoints (terminations at your ignition switch and fuse block). Mine had an obsolete fuse block and two burned terminals, so, I replaced it with a new, aftermarket one. If your melting/burning is limited to the fusible link mess, maybe you won't need to pull the harness.

- those inline ammeter fuses are soldered in, so if they're not blown, you can leave them intact and examine the rest of the lines to the ammeter for issues.

- About your 50 amp meter, unlike the earlier 30 amp meter wiring, that full charging current doesn't flow through the meter. But, it does still route 12v through those ammeter lines, so when you pull the cluster to check things, make sure you've disconnected the battery.

- Those 50 amp meters are easy to fry if the PO removed the fusible link and thought full charging current needed to go through that meter. I think that's what happened to mine.

- The good news is new clusters (50a meter and km speedo) are cheaper than a replacement 50a meter. I picked up an aftermarket metric cluster and plan to use the new one, with it's new 50a meter, but swap in my old speedo/odometer. Haven't done it yet, but seems like that should work.

Good luck!
 
swamp-thing said:
Thank you! I did check both the Ammeter fuses and they are not blown ( hoping that's good news! )
This truck had a plow and some hokey plow related lights and BS on it so I’m leaning in that direction as to what may have caused the original issue……
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That's good. Probably a short to ground somewhere along that WL line caused the melting. Hopefully it's just around the fusible link area. But, checking those other WL terminations will help scope the work required. You'll also want to check your alternator for proper charging after the "incident", whatever it was.

I forgot to mention that if you do happen to find melting at your fuse block and/or ignition switch, there are harness connectors at the firewall, just above the passenger foot well that should also be checked for melting. Pretty easy access.
 
For those who've been following along I'm pretty curious about what everyone is doing by way of replacing or mildly upgrading battery cables.

Re: the recommendation for HD cables from Fourrunner -- I’d planned to swap in new cables even before this fiasco.
And while I run big heavy duty cables on our diesel truck, I really do want to try to stick with something near to the OEM setup if possible.

This cruiser is too original in lots of other ways (clearly not the wiring I'm dealing with at the moment) to go with full military cables.

Any decent OEM-ish recommendations?
I'm totally good with heavy gauge cables if they resemble something along the lines of the stock config...

TIA
 
swamp-thing said:
For those who've been following along I'm pretty curious about what everyone is doing by way of replacing or mildly upgrading battery cables.

Re: the recommendation for HD cables from Fourrunner -- I’d planned to swap in new cables even before this fiasco.
And while I run big heavy duty cables on our diesel truck, I really do want to try to stick with something near to the OEM setup if possible.

This cruiser is too original in lots of other ways (clearly not the wiring I'm dealing with at the moment) to go with full military cables.

Any decent OEM-ish recommendations?
I'm totally good with heavy gauge cables if they resemble something along the lines of the stock config...

TIA
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Not sure what's OEM spec, but I made up a couple of awg 2, tinned, copper, stranded battery cables and ends.

They seem to work well cranking...once all the connections/grounds were cleaned and squared away. Which, in my case, made a huge difference.

I found this pic of the cable/end, and the new fusible link pigtail from @Coolerman.

Those blue tape labels helped me keep things straight during the rewiring process.

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