Fusible link and fuses issue (1 Viewer)

[oUZIo]

My 40 is consuming a lot of my time and the is getting jealous.
Long story short, had to take off the alternator to replace a radiator hose. After I got done I tried to reconnect the +iv back to the battery, as soon as the connection was made, smoke came from the fusible link area (not sure if it was the link or the fuses). All fuses in the picture (two in the black box, one in the while tube) were blown as well, and of course no power when I tried to turn key. Tried replacing the fuses and reconnecting one more time and one of the black box fuse blew again... and here I am for help.

I have a three questions...

1 - What is the correct amp and purpose for each fuse? Since I tried replacing the blown ones I am not sure which amp goes where, know all three are different amps.

2- How do I test the fusible link? to check if it survived.

3- How do I troubleshoot this issue. I expect a short somewhere and here is some context... Between detecting a cooling issues and waiting for parts to arrive I grounded the idle solenoid... Parts arrived, changed the thermostat, fired her up, it ran for 10 minutes before I detected another leak, parked her back in the garage... Disconnected +iv cable, removed alternator, replaced radiator hose and put everything back together. When I tried to connect the battery cable back I experienced this new issues. So I am expecting solenoid or alternator wiring, or I might have messed up with some other wiring while trying to yank out radiator hose.

 

[edwjmcgrath]

My 40 is consuming a lot of my time and the is getting jealous.
Long story short, had to take off the alternator to replace a radiator hose. After I got done I tried to reconnect the +iv back to the battery, as soon as the connection was made, smoke came from the fusible link area (not sure if it was the link or the fuses). All fuses in the picture (two in the black box, one in the while tube) were blown as well, and of course no power when I tried to turn key. Tried replacing the fuses and reconnecting one more time and one of the black box fuse blew again... and here I am for help.

I have a three questions...

1 - What is the correct amp and purpose for each fuse? Since I tried replacing the blown ones I am not sure which amp goes where, know all three are different amps.

2- How do I test the fusible link? to check if it survived.

3- How do I troubleshoot this issue. I expect a short somewhere and here is some context... Between detecting a cooling issues and waiting for parts to arrive I grounded the idle solenoid... Parts arrived, changed the thermostat, fired her up, it ran for 10 minutes before I detected another leak, parked her back in the garage... Disconnected +iv cable, removed alternator, replaced radiator hose and put everything back together. When I tried to connect the battery cable back I experienced this new issues. So I am expecting solenoid or alternator wiring, or I might have messed up with some other wiring while trying to yank out radiator hose.

It sounds like you've got a dead short somewhere. Why you are blowing both the fusible link and two different fuses, I don't know. Testing the fusible link is pretty simple if you have a volt-ohmmeter. Put it in resistance/ohm mode. Measure the resistance across the FL. 0 is good. Open is bad.

What do you mean that you " grounded the idle solenoid"? This doesn't sound right. Why would you do that?

 

[1MAC]

While I have no idea what you have done, the fusible link should be easy to test. It burns up if you have a short, so just test to see if you have continuity on both sides of it.

BTW, nice username and hometown. Who else on here has a subgun in their username AND lives in KC????

 

[Pin_Head]

Did you hook up the battery backwards?


The two fuses are for protecting the amp meter when the fusible link blows.

 

[oUZIo]

What do you mean that you " grounded the idle solenoid"? This doesn't sound right. Why would you do that?

That was for working on another issue, I will be taking that back to normal before I troubleshoot this first.

 

[oUZIo]

While I have no idea what you have done, the fusible link should be easy to test. It burns up if you have a short, so just test to see if you have continuity on both sides of it.

BTW, nice username and hometown. Who else on here has a subgun in their username AND lives in KC????

Well hello neighbor! looks like you have a nice blue project going on, driveable?

 

[oUZIo]

Did you hook up the battery backwards?


The two fuses are for protecting the amp meter when the fusible link blows.

Hey pin head, I am sure it is something stupid but no, battery was not connected backwards... as I only disconnected the +iv

 

[Pin_Head]

Did you connect the large white wire to the alternator case? Whatever you did resulted in a massive short.

 

[oUZIo]

Did you connect the large white wire to the alternator case? Whatever you did resulted in a massive short.

I think I have all the wires connected the right way, I think .
I will replace the fuses, completely disconnect the alternator and then try to reconnect the terminal, this way I eliminate any other short possibilities.

Need to get extra fuses first... Any idea what amp fuse goes where?

 

[bj40green]

The 2 fuses are 5Amp each.
The fusible link R means 0.85 mm2 or AWG 18. This protects circuits wired with AWG 14.
You have a massive / solid short. Find that short first with an ohmmeter before you start replacing fuses.
Here is a part of a wiring diagram.


For more info and how to make one yourself in my thread: -► https://forum.ih8mud.com/diesel-tech-24-volts-systems/526232-fusible-link-one-my-78-bj40.html

Rudi

 

[oUZIo]

The 2 fuses are 5Amp each.
...
Rudi

Thanks Rudi,

Any idea on the fuse on this one, and what is this for?

 

[bj40green]

That connector is part of your fusible link.
The WL (White/Light Blue) wire on the bottom side goes to the B lug on your alternator.
The other side is the fusible link and ends up at your battery + post.
See/follow the blue line in this pic.


Rudi

 

[lostmarbles]

Just to be clear.

Something you did created a big short-circuit that blew your main fusible link when you reconnected the battery. So, as others have said, you MUST find that short-circuit and remedy it first. (Positively and not vaguely)

Blowing one of the little 5A ammeter-protection fuses was just an inevitable result of the blown fusible link. Because with a gap in the fusible link wire, all the current that was previously flowing through that link would have tried to flow through your ammeter (which is only rated to take milli-amps and so the fuse blew to protect it).

 

[oUZIo]

Did you connect the large white wire to the alternator case? Whatever you did resulted in a massive short.

Pin Head, I think you were right on this one!
I disconnected the alternator yesterday, but looking at the shape of the wire connector I can see how it could have ended up touching the alternator case upon tightening the screw.

I replaced all three fuses and alternator is connected back, no smoke or sparks and I see life when the turn on the key (will start tomorrow after I fill it up with coolant).

 

[oUZIo]

FL was also bad, had to hack it up for testing. I don't intend to drive like this but I think it is safe for right now? Will be ordering a new one as soon as I find one.

Thanks for all the advice by everyone! There is no way I would have been able to troubleshoot this without the help on this post, and helpful information on other mud posts.

 

[1MAC]

I hope you flipped that ring connector over! That thing touching the alternator case would definitely explain your blown fuses and link.

 

[bj40green]

Hi UZI, good trouble shooting!
So that ring connector touched the alternator housing?


Rudi

 

[oUZIo]

Hi UZI, good trouble shooting!
So that ring connector touched the alternator housing?

Rudi

Yes sir! I was able to put everything back together without any issues so I suspect pin head was right.

Since the alt wiring appeared to be correct, I kept looking for a loose wire creating the short, something I knocked loose while trying to work on the rad hose. I also came across another website post, the guy ran into the same issue due to the same cause - http://zilvia.net/f/engine-tech/423718-alternator-fuse-keeps-blowing.html

 

[Lank]

Where is this FI located?

 

[JJWA40]

Man I love this forum. It’s amazing what you can find. I’m bought my FJ40 5 months ago. Ammeter didn’t work and this thread gave me everything I needed to fix the problem. Thanks so much!