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Discussion Starter #1
Driving home the other day all three windshield wipers stroked to an upright position and stopped, along with the engine. Putting the truck in neutral I coasted to the side of the road. Some of the electrical in the truck worked, but all circuits that would be hot in the”Run” Key position were dead. Fuses in the engine bay relay block (EBRB) looked good. Removing the clear plastic window on the 120 Amp Alt fuse showed it was open. Not blown, but cracked near the center fuse area. Inner fender wells are not alone.



Fuse already replaced in photo

I tried to pull the fuse straight out without any luck. By pulling with a bit more force with some needle nose pliers I removed the white plastic housing bent the leads together a secured with an alligator clip. This allowed me to get the truck back to the house.



Looking for information I found this thread. Main Fuse Blown- How to Change?

I bought a fuse at local parts store for under $5



I played with trying to pull the block out of the lower case but could not raise it out of the box so everything came off or out. I removed the battery for room (already disconnected for safety) and removed ground from inner fender.




Disconnected DRL relay block box on firewall side of EBRB by inserting small screwdriver blade in opening along DRL box to release tab and lift (wiggly) DRL box.



Then I removed three bolts attaching EBRB to the truck and cable from alternator.



Also removed the alternator cable restraining clip by depressing sides and lifting up.



Unplugged two connectors on engine side of EBRB and clipped two tie wraps holding harness to EBRB.



Released relay/fuse block from box by moving inner tabs in four holes towards the center of block while lifting block assembly. n0idx80 used the battery J-bolts as hooks to lift.





Lifted the box up and towards fender then moved box towards engine and off block assembly while moving block assembly up out of box. I held on to the wiring harness along fender to help move the box away from fender mount point and down.
Now the block assembly was out of the box and I removed the lower gray plate from the two block assemblies. It is clipped on at two, maybe three points.



The two block assemblies could now be separated by releasing at two locations, by pressing a thin shaft down along edge slot raising rear and lowering the front.




Finally I unbolted the fuse with an 8mm and 10mm socket.




Then I reversed to reinstall. Installing new cable ties before reattaching the box.



Make sure filler pieces and interlocks line up between block assembly and box.






This is what I did to replace this fuse, almost 3 hours of time. Hope if you need to deal with this fuse, you find this posting and it is of help to you.
 

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That's a ridiculous amount of work. Booooooooo Toyota !
 

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Discussion Starter #5
Do you know what caused the fuse to break or blow? Did the fuse or the holder crack due to stress?
I think I now have an idea of what happened. The fuse itself broke, the flat strip of metal inside the fuse cracked. It did not melt or separate at the soldered center point. Around 9 months ago I installed a "Mean Green" alternator rated at 200 amps. I believe the higher current caused the metal to become brittle and crack. After installing the new fuse I found it melted down. I think the OEM fuse handled the heat better than my replacement.


Before


After​

It still works but I need to replace it again. I measured 148 amps passing though the fuse when I started the truck. It took 4 minutes before it dropped below 100 amps and the batteries were not that low. I am going to run a 4 gauge cable from the alternator to the main battery with a 200 amp fuse along with the existing alternator cable to allow the current flowing to the battery to bypass the 120 amp fuse.
 

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Good assessment. I am not surprised as deviating from the Toyota engineering usually causes this type of thing. With electronics, suspension, etc.
But you have analyzed and figured out the upgrade. Kudos.
 

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Friend was helping me drink beer and replace my tensioner assembly. We got to talking and forgot to disconnect the battery.... One thing lead to another and the fuse blew after an exciting firework show under the hood. I'm 1/2 way through this right now and I cannot express how much this thread is helping me. I had no clue a fuse/relay could be so hard to replace. Thanks again!


-On the run posting uselessly tinny pictures
 

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Damn it was trying to fix a stuck solenoid on my new winch (of course working on it without disconnecting the battery,why would one do that) anyway, pop, ergggggggg blow the 120 amp fuse. Bent the prongs together so I could get to work, and now have to look forward to dealing with this horrible design from Toyota to change the fuse. Soooo looking forward to this.
 

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Blew my main fuse, and have a temporary fix in place, but was wondering if anyone had considered replacing this whole assembly with an inline 120A DC manual reset circuit breaker... That sounds a whole lot easier than this disassembly of the whole fuse box (which I am not looking forward to...)
 

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The fuse failed from thermal fatigue, rather than overload. The more heating/cooling cycles a fuse sees, and the greater the temperature rise per cycle, the greater the probability of a fatigue failure. Of greater concern would be the 150A current through the fuse.

1. Are there any other non-stock accessory loads present at startup, or is this all battery charging current (plus brake accumulator pump for the first 5-10 seconds)?
2. How did you measure the 150A current? Clamp-on DC ammeter?
3. Are both batteries being charged simultaneously?
4. Have you checked alternator voltage at startup? It seems it would have to be higher than normal to drive this much current.
 

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Bump .... any one else?
 

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So hard to replace. Still cant separate it. Dont know what to do. Fuse box is getting damaged just to try and separating it.
What I did and it worked for along time is remove the plastic top out of the bad fuse and bridge it with the new fuse. Press down and it will lock in place. Did this when it blew on a trail and worked for a year until I replaced it.
 

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Thank i did that too just to get it in my ggarage. But i finally got it separated. But damn got the wrong fuse. I noticed when i was installing it that i bought a 32v 120amp. Do you all know what the difference between 12v and 32v fusible link?
 

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Tried everything...can't get the boxes out of the actual fuse box!!! I depressed the 4 tabs and used the J bolts like recommended and have had no luck. Cracked my box in the process. Any advice would be appreciated!
 

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Tried everything...can't get the boxes out of the actual fuse box!!! I depressed the 4 tabs and used the J bolts like recommended and have had no luck. Cracked my box in the process. Any advice would be appreciated!

Use gift cards in between the layers to make sure the tabs stay depressed. And the main thing is relax and have patience. You don't want to break something because you got cranky!
 

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Can you please elaborate on the gift card technique? I'm having a hell of a time getting the top half of the fuse box to separate!

-B

Use gift cards in between the layers to make sure the tabs stay depressed. And the main thing is relax and have patience. You don't want to break something because you got cranky!
 

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Did anyone have a problem removing the fuse block from box? I am using a small screw driver to shift the tabs inward and when I try to lift the block out of the box the whole things rises. Anyone else have this problem? How did you solve it?
 
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