rigtec
New member
There are a few more but a lil' hard to point out. The point is I believe that Toyota assembled the outerbox first, built the Busway grid, THEN pulled the wiring harness (conn. first) through the basin and snapped it; locking it in. Okay, that's one theory. Here's what can be done about a blown alternator main fuse. Since you can't really access this fuse we'll need to approach it another way. First here's Toyota's wiring scheme...
If you look at the alternator (Top) and follow the pink trace to the main engine wire lug at the upper right-hand side, you'll see the Line side supply bus just to the left; still in Pink as it travels down twds the 140A main fuse (which I have traced in Blue)! This fuse is referenced, number 12:140A Alt (For high current) "See Item list in the upper left corner"! Once this fuse is blown, you'll lose a few accessories e.g., courtesy lights, ECU, mayday, Radio, Amp... But the main thing that will be lost is the alternator's ability to charge the battery because that fuse's primary function is to disconnect the battery cable in the event of a major front-end collision to prevent an explosion; if you follow that line you'll see that the fuse is too large to protect anything else... all of those circuits that tap that fuse (through the Load-side supply bus) have their own, appropriately sized fuses. Here's a different schematic to give another P.O.V. :
This one gives the Charging circuit vantage point. And again I have the alternator's B-Term and supply cable traced in Pink, the 140A Alt fuse traced in Blue, and the Battery cable in Yellow so the risk of a mistake is minimized! The most practical way to restore power to those circuits lost due to a blown main fuse is to by-pass it using the exact same thing... a 140A in-line fuse. The connection points are very simple. Just make your own wire harness with a 140 amp inline fuse built-in like this one:
You can use any kind of fuse that you feel comfortable using e.g., wafer, cartridge, CB (Circuit Breaker 'pictured above')... Actually, I'm already using this method... NOT to resolve a blown fuse, but a parallel (partner) supply line for quicker battery feeding when using Over-sized alternator, High current accessories; know as "THE BIG THREE", if you've already implemented this wiring configuration then you've already by-passed (Jumped) your 140A Main Alt fuse! To jump a blown line fuse, you can terminate between the POS (+) battery post and alternator "B output" terminal. Or, you can grab the alternator output lug right in the engine room fusebox, "see red arrow":
The blue arrow is the 140A fuse... this may be positioned a little differently than your truck; 4'th gen, but everything else relevant is much the same! I meant to show you how the fusebox "Busway template" is configured internally...
Not much to see here but it is interesting how they fit it all in there
hwell:
Anyway, if you ever blow this fuse at anytime for any reason you'll have to decide how you'll go about getting it repaired... a Fused jumper-line may be a viable alternative to the dealership, hope you'll find some portion of this thread helpful!
Best to you!
If you look at the alternator (Top) and follow the pink trace to the main engine wire lug at the upper right-hand side, you'll see the Line side supply bus just to the left; still in Pink as it travels down twds the 140A main fuse (which I have traced in Blue)! This fuse is referenced, number 12:140A Alt (For high current) "See Item list in the upper left corner"! Once this fuse is blown, you'll lose a few accessories e.g., courtesy lights, ECU, mayday, Radio, Amp... But the main thing that will be lost is the alternator's ability to charge the battery because that fuse's primary function is to disconnect the battery cable in the event of a major front-end collision to prevent an explosion; if you follow that line you'll see that the fuse is too large to protect anything else... all of those circuits that tap that fuse (through the Load-side supply bus) have their own, appropriately sized fuses. Here's a different schematic to give another P.O.V. :
This one gives the Charging circuit vantage point. And again I have the alternator's B-Term and supply cable traced in Pink, the 140A Alt fuse traced in Blue, and the Battery cable in Yellow so the risk of a mistake is minimized! The most practical way to restore power to those circuits lost due to a blown main fuse is to by-pass it using the exact same thing... a 140A in-line fuse. The connection points are very simple. Just make your own wire harness with a 140 amp inline fuse built-in like this one:
You can use any kind of fuse that you feel comfortable using e.g., wafer, cartridge, CB (Circuit Breaker 'pictured above')... Actually, I'm already using this method... NOT to resolve a blown fuse, but a parallel (partner) supply line for quicker battery feeding when using Over-sized alternator, High current accessories; know as "THE BIG THREE", if you've already implemented this wiring configuration then you've already by-passed (Jumped) your 140A Main Alt fuse! To jump a blown line fuse, you can terminate between the POS (+) battery post and alternator "B output" terminal. Or, you can grab the alternator output lug right in the engine room fusebox, "see red arrow":
The blue arrow is the 140A fuse... this may be positioned a little differently than your truck; 4'th gen, but everything else relevant is much the same! I meant to show you how the fusebox "Busway template" is configured internally...
Not much to see here but it is interesting how they fit it all in there
hwell:Anyway, if you ever blow this fuse at anytime for any reason you'll have to decide how you'll go about getting it repaired... a Fused jumper-line may be a viable alternative to the dealership, hope you'll find some portion of this thread helpful!
Best to you!
Last edited:
