A non-fuse blowing short (Fusible Link)

[60 toy ota]

At least that's what it seems to be.

Assuming the wiring between the '81 diagram holds true for an '84, the problem lies within the circuit with the white fusible link, which includes the alternator, and fuses engine, defog, A/C, Stop, headlight cleaner (no fuse) tail, and dome, in that order. we can rule out the engine because I now have a stand-alone fuel injection harness, and the original engine harness plugs are capped and out of use, minus the +12v for the old distributor which is currently used to throw a relay for the FI.

It's also an intermittent problem, so it's been tough to narrow down, but when it's present i know this so far: When I jump the inspection light between ground and the dome or tail fuses (EDIT: turns out this happened with all of the listed fuses, but like I said, it was an intermittent problem), everything in that fusible link looses power. when I take the light off, power is not immediately restored (restoration time not consistant) and no fuses are blown. during this time there is no power at the alternator charge terminal (engine off).

part of this seems characteristic of a fusible link, but how could grounding a hot wire via a known good light ever be a problem? should I try to find the joint where the white wire splits to become either the dome or tail circuits?

 

[jawjatek]

That does not sound like a short circuit. A short circuit is, for example, when a power wire is touching ground due to some fault, and the resultant excessive current is blowing the fuse.

What you're describing (not very clearly to me, sorry) sounds like there is a high resistance in the circuit that is dropping all the voltage when you put a load on there. Check the fusible link for high resistance - it should be very low, like the piece of wire it is.

Hard to say because I don't really follow your description.

 

[Randy88FJ62]

Tail lights: Check rear quarter panels. Water can get in and corrode wires over time causing increased resistance.

Dome Light: Take off plastic lens and visually inspect the contacts. Excessive corrosion caused from the arc when switching could increase resistance.

Rear Defog: Wire connecting to rear tailgate hatch defog wires may be loose?

 

[60 toy ota]

thanks for the replies.

Check the fusible link for high resistance - it should be very low, like the piece of wire it is.

sorry for the poor description, it's also kinda hard to describe haha. I agree about the high resistance, but if it were the fusible link that had the high resistance, shouldn't it not matter which fuse I put the light to? (wouldn't I get the same result for each fuse I put the light to on that circuit?) EDIT/UPDATE: Yes I would, and when I tried later on the same thing happened with the rest of the fuses on that FL.

Tail lights: Check rear quarter panels. Water can get in and corrode wires over time causing increased resistance.

Dome Light: Take off plastic lens and visually inspect the contacts. Excessive corrosion caused from the arc when switching could increase resistance.

Rear Defog: Wire connecting to rear tailgate hatch defog wires may be loose?

say the issue is, for example, corrosion in the rear side markers. I have a hard time seeing how turning on the dome lights (with the tails on or off) would cut the power in the circuit. Unless, of course, the same problem existed in the dome light, but I find it very hard to believe this same problem would show up in two places at the exact same time.

 

[60 toy ota]

Update: caught the circuit while it was in a good mood and decided to take a few laps around the block. I didn't turn on the domes or the running lights, but as I was driving I noticed I wasn't getting any charge from the alt, I was just slowly draining the battery as I drove. by the end of the drive my volt meter was almost at 0. earlier in the day it was at 16 with the engine running. because the alt. and the fuse block are both on the same side of the fusible link, I'm starting to suspect that it may in fact be the F.L. going bad, causing the alt. to give power to the car but not charge to the battery. does this sound logical?

 

[jawjatek]

Yes, check it out and tell us what you find.

If it isn't the acme of foolishness, can you go over the problem symptoms again? Is it an intermittent issue with the dome light, AC, or all? Also sum up what you've found or measured so far. Like: how did you know you were slowly draining the batt? You have a voltmeter, or some instrumentation on there, voltage steadily dropping, faster with the lights on? With engine on there should be @14 VDC at battery...what does "jump the inspection light between ground and the dome or tails" mean? (sorry, not clear.) You say there's a delay? Noting on the car could cause a delay I can think of... also not clear.

Assuming your charging system and voltage regulator is healthy and within op limits, it does sound like you have an intermittent or failing "open circuit" or high resistance due to conductor nicks, mechanical stress, or bad connection from rust or something. Physically inspect all of it, and measure the resistance of that FL. Or just use the shotgun approach and either replace or temporarily bypass the FL. All I got right now.

 

[60 toy ota]

I think a video will explain what's going on much better than I could, so I'll upload one in the next hour and let the footage speak for itself. But to answer your question, I first knew I had a problem when I got in the car the other day and it wouldn't start, just a strong crank. After trying to run the fuel pump at the diagnostic port, I realized I also had no power to my FI relay (via the old 2f distributor wire), my climate control fan, tail lights, dome lights, and brake lights. when I was driving the car the other day, I had a friend with me for the ride who wanted to try driving stick for the first time (so why not, right??) and of course, she killed it, and the starter didn't even have enough juice to turn the engine over. gave it a rolling start and drove the few blocks to my house, all the while the battery gauge was all they way down. My dad has a multi-meter I can borrow when I visit home this weekend, but as a college kid I don't have anything fancy like that (...yet, there is a harbor freight here in my town...).

 

[60 toy ota]

 

[60 toy ota]

Weeeeell I think that settles it...anybody have recommendations for a replacement fusible link?

 

[81Red60]

I literally just went through this same problem. I ended up making my own with some 18 and 20 gauge fusible wire I got from amazon. I am trying out some weatherpack connectors to see if I can make a replaceable fusible link.

 

[60 toy ota]

. I am trying out some weatherpack connectors to see if I can make a replaceable fusible link.

Ooh I like that idea, what do you think about them so far?

 

[81Red60]

The only problem is they come in set sizes for the different gauges. You want to go 4 gauges more for a fusible link than the primary wires so you would have to use two different size weatherpack connectors. I am going to see if I can double up the stripped portion of the fusible link wire and soder them securely into the pin connector. In the mean time I used some waggo lever nuts that work great.

 

[60 toy ota]

So I'll be replacing it the fusible link as soon as it's not raining, but in the meantime I want some opinions. I was wanting to just buy some fusible link wire and reuse the old connected to save money, but when I took a closer look I think the connectors may have been the problem. These pictures were taken as I first saw them. In the 1st pic, dues anybody know what this connector goes to?

 

[81Red60]

I agree that the connectors probably need to be replaced also. My problem, which you will have, is that I could not find an OEM replacement a since the PO cut them off the battery cable and wiring harness. Someone suggested the weatherpack connectors on here earlier which I am going to try.

 

[60 toy ota]

Okay so I rebuilt my fusible link for use until the new one comes (Saturday) and then afterwards as a spare. I'm concerned about this huge burn that you can see in the picture, what would cause that much heat at the connector? There was corrosion at the white connector, but no corrosion at that connector so I wasn't expecting any issues around there

 

[FJ62gator]

Any excess current through the link will cause the burn around connectors. You may want to monitor your temp fix to see if you have something wrong downstream before putting in your replacement.

Fuse Link

• FJ62gator
• Apr 4, 2017

I rebuilt the fuse link to the ignition system using a 14 gauge fusible link wire from Bussman...

I just finished my saga with a fusible link on my '89 FJ62 this evening. A few months back I hooked up jumper cables backwards, melted the fusible link to the ignition system and blew a handful of fuses. It destroyed my nearly new optima battery (thank goodness for the warranty). I had a sound guy put in an 8 gauge inline fuseholder with a 40amp fuse as a temporary measure, but this circuit regularly sees more current going through it than 40 amps, so it would blow and literally melt a black hole in the fuse. At the time I was building a house and didn't have a garage, so i rode around with a pocket full of fuses. Fast forward to this past weekend, I broke out the service manual and reverse engineered a fusible link. I bought a 14 gauge fusible link wire by Bussman on Amazon and some ring terminals from the parts store. It's a different style link than yours, but just as frustrating.

 

[BrewsCruise]

I am trying out some weatherpack connectors to see if I can make a replaceable fusible link.

I'm also rebuilding my fusible link as the OEM one is non-existent on my FJ62. How did the weatherpack connectors work for you? I'm looking at getting the correct inserts for each gauge wire, but not sure if they will snap together with the whole connector.

 

[81Red60]

The problem I found while researching the weatherpack connectors was they were not built to connect wires that are different by 4 gauges as the fusible link requires. What I did find were wago connectors that can accept a really wide range of wire gauges and they are acceptable for use in automotive/under hood wiring. I have the new fusible link in for almost 6 months and it has worked perfectly. I say this as an amatuer and am open to any feedback to anyone else that is more knowledgeable in the subject.

 

[OSS]

WeatherPak connectors are woefully inadequate as a fusible link plug. They are only rated to 20 amps. When all the accessories are running in the car (fan full, lights etc) more than 20 amps can run through the harness.

The gold standard for 12 volt wiring is done on yachts and boats. Zero yachts use fusible links. It's all fuses & breakers. A fusible link is a cheap compact way for automobile manufacturers to squeeze in a fuse just before the positive terminal on the battery.

The only redeeming feature of a FL is that it's small. That's it.

Slow blow fuses or circuit breakers. That's the answer. Think 40amps.

With that all being said - I still have a FL in my 60.