Ritzy4Runner

iTrader: (1)

Searched for some answers to my son's '90 4runner issue. No Power to anything!

Seems he pulled into his driveway after being out and about. Went to roll up his driver's side window and when it reached the top of the track is does bog down. when it did, he heard what sounded like rumbling coming from the engine compartment and noticed his AMP meter started spiking in the 18 VDC direction repeatedly. He thought nothing of it and went inside.

The next day he got up to go somewhere and when he turned the key ... NOTHING, no lights no dash gauges no warning buzzer ... zilch! Call Dad

Investigation lead me to believe we must have a blown fuse somewhere, so I got out my FSM for the 1990 4runner (*another story of a rescue from the bone yard) and looked up the power diagram.


As you can see from the diagram, I checked all the main fuses, the 30 and 40 amps the 80 amp was also checked and found to be good. The only thing common to all of these left the Main Fuse which is supposed to be right after the battery. Not fully understanding what they called the "Main" fuse in the FSM is actually the fusible link. I checked the location in the FSM which said it was located right next to the main fuse panel. After some searching here on Yota Tech, I discovered that the Main fuse is actually called a fusible link.

Now knowing what I was supposed to be looking for I tried again but still did not fully understand what it was supposed to look like. My previous experience with fusible links was many years ago and it was like a regular fuse but was a small bar in a holder. Well I could not find it anywhere. After a quick search query on Yota Tech, I found out it was a wire that ran from the main fuse panel to the positive lead of the battery connector.

When I started checking the connections, I discovered that the fusible link had been vaporized! I had a connection on the positive side of the battery terminal but it was only about 2 inches long. There was also another wire that came from under the main fuse panel in the front that had some rather interesting looking insulation. This had been my fusible link.

Armed with the knowledge of what the freaking thing looked like I went in search of the next replacement part at my local bone Yard and as luck favors the fortunate, I located two 90's vintage 4runners and acquired a replacement fusible link. Very easy to remove intact provided the previous yank-a-part artist didn't just cut wires from the battery or the fuse box.



I can not stress this point enough, you MUST use the designed fusible link for your 4runner. If you use other then designed fusible link, you can start a fire. These are not just pieces of insulated wire, they are specifically designed to MELT at a predetermined current loading. They are also covered in a special type of insulation designed to work with these wires. They help to contain the melting wire without igniting from the heat generated from the melting of this designed wire. If you use normal wiring of the same gauge (which is smaller the the connecting wire on either end of the fusible link) an overload will cause the wire to melt but at a temperature higher then the fusible link which can result in damage to the components of our trucks as well as the high probability of an engine fire. DO NOT cut corners on this wire. It is the same thing as replacing one of the normal fuses in our fuse panels with a higher rated fuse, you will fry something and in this case is could very well be your truck!

First item to do is to remove the battery.


If you have not previously done so, remove the fuse panel cover. Then remove two 10 mm screws securing the fuse panel to the right fender well.



Pull the fuse panel free of the fender. The forward mount also has a small locating tab so be gentle when you try to pull it free.

You will note two small clips on the front base of the fuse panel. These are the lockdowns for the lower cover. Using a small flat blade screw driver, gently lift these up while at the same time moving the bottom cover downward. Once both clips have been removed the bottom cover will be free from the front side. The rear of the cover is hooked over the bottom latch at the rear of the panel


Swing the cover clear and unlatch it from the back location. This may be difficult due to the wire bundles near the rear of the fuse panel.


Remove the bottom cover exposing the underside of the panel.


Removal of the fusible link wire from the 80 amp fuse requires removal of the fuse. This fuse is held in place by a locking block. near the rear of the mounting location you will note what looks like a clip.


Push the clip towards the edge of the panel while pushing the 80 amp fuse downward.



Fully pull the assembly from the bottom of the panel.


One side will have two small phillips/hex screws. This is the pair of screws that hold the fusible link to the fuse and are 8 mm. I recommend using either a wrench or socket to loosen and removal of those screws. If you are only replacing the fusible link then skip the next step as removal of the single 10 mm screw is not necessary.


If you are going to replace the 80 amp fuse then remove the single 10 mm screw on the opposite side in the same fashion.


The fusible link is now removable from the system. Attach the new fusible link in the correct location on the fuse with the other two red wires using the 8mm screws removed previously.


If you replaced the 80 amp fuse, finish up the replacement by installing the other white wires on the opposite side and secure. Insert the assembly into the same location from the bottom of the fuse panel.



Continue pushing from the bottom until it is fully seated. You should hear a slight audible 'click'.



Position the fusible link wire under the panel towards the front cutout. Fit it into the cutout and then attach the bottom cover and snap into place. This will secure the fusible link in the panel.


Remount the fuse panel with the two 10 mm screws, attach the loop end of the fusible link to the POSITIVE (+) terminal battery cable and secure it firmly to the connector.

Reinstall the battery ensuring that the NEGATIVE (-) terminal post is closest to the right side fender, the POSITIVE (+) terminal post is towards the engine. Connect the negative terminal first and hand tighten. Attach the positive terminal and hand tighten. You have now completed your fusible link installation.

* The story behind how I got my copy of a 1990 4runner FSM is a rather strange coincidence. About a full year before I even saw my son's 90 4runner at auction, I had been in my local bone yard looking for some new/old part. They had a 1990 4runner in for disassembly due to an engine fire ... fusible link may be?? anyway in the floorboard of the rear seats which were completely filled with water, wonder how that got there submerged was not only volume 1 but volume 2
Needless to say I was bummed but thought I could rescue those! yeah was I in for a treat. I asked and the guys said "Sure you can hav'em". What I didn't realize at the time is I would spend MANY hours over the next two weeks drying out the pages of both manuals. That was a 'fun' project. the biggest problem was the pages are very thin and if you don't get them separated quickly they tend to 'weld' together. I encountered this during the initial separating process as the pages started drying out as soon as I had removed them from the flooded floor boards.

I was able to put paper towels between each and every page (there must be over 1000 pages in Volume 2 alone )and would then help the drying process with a hair drier and eventually I had both volumes of the FSM. They have been indispensable since I acquired my son's 1990 would I do that again? Well I don't know

BigBluePile

iTrader: (3)

Nice write up, and great save on the FSM!

weaselman

are you going to replace the alternator as well? sounds like the voltage regulator shorted out.

had this happen to me. all of my dash lights got really really bright and my windows worked amazingly fast. haha and then the alternator just died. didnt have the fusible link blow tho.

dropzone

iTrader: (6)

good fix and nice write up...Glad to hear that we had the info here to also help out!
in case the fsm gets wet again you can download it here:
http://ncttora.com/fsm/index.html

Ritzy4Runner

iTrader: (1)

Well with the fusable link seeming to be the main issue I don't beleive I will need to replace the alternator. After install we started up the truck and ran it for at least 20 minutes, system getting up to operating temp and checking all electrical systems. The amp meter was reading a solid charge of around 14-15 volts. I also replaced the short ground leg from the battery terminal to the inner fender well wall just forward of the main fuse panel on the fender well. I will have my son continue to monitor the electrical for any thing new. Thanks

Thanks for the link but I have the manual now. I may need some diagrams for some later 4runners such as a 2000 or 2002. Once again thanks for everything. I try to give back in my write ups

Kiroshu

Wow very interesting. Very great job btw. Thats not a common issue on these trucks.... Interesting....

Ritzy4Runner

iTrader: (1)

Yeah but isn't nice to know that you can find alot of those "not very common on these trucks" fixes here? That's how I have found a few that have happened to me ... right here on YotaTech First you scratch your head ... then you do a few searches here ... and if that doesn't find it ask!

If it has happened to you, it most likely has happened to someone else

Is this a gr8 country or what?!

Kiroshu

^Lol yea i guess your right

ajax469

would the fusible just the front windows also or shut the whole rig down all together

wyoming9

iTrader: (1)

Nice write up but are you sure those are M8 bolts /screws holding the part in the ones on my 87 4Runner where M4 I guess they could have increased the size.

M8 are the same size that are in the thermostat housing .

I hope it cured the problem

weaselman

the WHOLE truck will die, you can always check the fuse tho.

little_red

i know this in an old thread but i think i just have found my answere to my 94 having totally no power..
pretty much same thing happen to me.. no power, no lights, radio, no door lights, no buzzing etc..

httpsteve

help.... when I opened my fuse box to change the alt fuse (took all apart..1st time) a
a slim copper piece fell out. hooked arrow on one end... looks broken on other end. About 1/4 inch wide, thin and about 2inch long


I thought maybe the main fuse link... but I get dash light and it turns over it just wont start, like when a ground is missing. I'm
thinking this piece was grounding something???

wyoming9

iTrader: (1)

A picture would really help.

Sounds like something broke .

Then who knows what people may have done before you.

dropzone

iTrader: (6)

Sounds like someone made a hacked jumper, sure you don't have a missing fuse?

DjShiznit

Hypothetically speaking, can this fusable link wire be extended between it and the fuse box with a typical wire safely? I ask because my truck had a 3.4 swap prior to my purchasing it. The battery had to be relocated to the drivers side of the vehicle. I believe the entirety of this fusable link wire was replaced with a standard, longer run of wire. I would assume adding wired to extend the length between the fusable link wire and the battery would not be a good idea, but should it work the other way around (between the fusable link and the fuse box)? If not, I'd assume anyone who has had to relocate their battery (and thus extend or replace this fusable link wire) could be in danger of having their trucks catching fire.

RJR

You should be able to extend the link with a wire of adequate capacity downstream (towards the fuse box) of the fusible link. The extension wire should have a current rating greater than that of the fusible link, so that the link opens before your extension wire. That way you are protected by the link all the way to the fuse box, and the sub circuits are protected by the individual fuses.

DjShiznit

OK thanks for the reply, RJR. I assumed as much, however I prefer not to take any chances, and value input on the issue. I'd consider myself somewhat electrical savvy however I do occasionally discover that I'm wrong and learn from the process. Before finding this thread, I had intended on running 8GA amplifier wire from the fuse box to the battery (to ensure plenty of power being fed to the fusebox). That may not be such a concern now that the fusable link may be the bottleneck. Any idea what gauge of wire should be sufficient to overcome whatever current rating the fusable link has? Being that my battery was relocated, I'd guess the total run length from battery to fuse box to be roughly 6 feet.

RJR

From the EngineeringToolbox.com, for single wires, the current capacity of various gauges is given as follows:
Assume PVC insulation and maximum 30 degC. Reduce these numbers for higher temperatures as follows:
•ambient temperature 31 - 40 degC: correction factor = 0.82
•ambient temperature 41 - 45 degC: correction factor = 0.71
•ambient temperature 45 - 50 degC: correction factor = 0.58

10AWG -- 52 amps
8AWG -- 75 amps
6AWG -- 95 amps

Note: These numbers are higher than the NEC stipulates for house wiring, largely because the NEC assumes 3 wires in a bundle, not just one. Thus the heating is greater.

Given possible underhood temps, I would think you would want at least an 6AWG wire to extend the link, and probably a 4.

Green

Thank you. I realize this is an old post but the write up and pics are the best I have seen in my search so far. My 92 is dead in a parking lot right now and I was scratching my head trying to figure how to get the 80 amp fuse out. The fuse-able link seems fine so I didnt need to go that far.

Truck is still DOA but at least know how to get the fuse out next time. I finally called it and used the towing/labor option of my insurance to take it to the dealer. (No time to research a good independent Toyota place with 12 miles of west Fort Worth.)

Great pics, thanks again.