Why is my in-line fuse blowing !?

Spike Strip

Let's Go Brandon !
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Buy a silver star subscription so you can post some pix of what you have and what's gone wrong. You're gonna spend way more than the $20 a year trying to figure this out the hard way.
 
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Now would be a good time to break out that Hongda multimeter :D. Seriously, once you figure out how to do a continuity test and voltage reading, you can diagnose almost any issue on a cruiser.

Are the fusing blowing immediately when you put a new one in?Or is it only after a certain amount of time? It sounds like there's a short somewhere, maybe after you rewired something rubbed through the insulation. I'm not sure what setup you have and whether it's stock, but a quick way of isolating the issue is to pull ALL the fuses from the fuse block, then start inserting them one at a time until the inline fuse blows. That will at the very least narrow down which circuit is causing the issue and save you a lot of frustration. You may not even be able to spot the issue visually, that's where the multimeter comes in handy.

(Edit: just re read your post to say it's only on ignition) Is it when you try and start the engine or when you just have the key in the "on position?
 
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Now would be a good time to break out that Hongda multimeter :D. Seriously, once you figure out how to do a continuity test and voltage reading, you can diagnose almost any issue on a cruiser.

Are the fusing blowing immediately when you put a new one in?Or is it only after a certain amount of time? It sounds like there's a short somewhere, maybe after you rewired something rubbed through the insulation. I'm not sure what setup you have and whether it's stock, but a quick way of isolating the issue is to pull ALL the fuses from the fuse block, then start inserting them one at a time until the inline fuse blows. That will at the very least narrow down which circuit is causing the issue and save you a lot of frustration. You may not even be able to spot the issue visually, that's where the multimeter comes in handy.

(Edit: just re read your post to say it's only on ignition) Is it when you try and start the engine or when you just have the key in the "on position?
I have my Hongda out and using it...so thank you...but to answer your Question ... no when I put fuse in is fine - I can turn on lights and honk horn etc..OBLy and ONLY upon turn of ignition does it blow.. how should I use my Hongda to diagnose?? meaning check what where..im sure if I sat and thought about it I would give myself my own answer, but its late and the last 4 days have been stressful to say the least.
so check continuity between the alt lines...volt at the ignition..volt at where then after that? I just dont know how to use it to narrow down whatever it is. walk me througusing the hongda correctly for this situation. help me learn for next time. thx
 
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I'd humbly suggesting not putting the OEM fusible link in there, but a decent resettable breaker - like a bussman. One advantage is it's easily resettable, other other is it can be manually tripped and used to disable the vehicle. I use 50 amps. The fuse is just for protection, it has to be pretty big because all the power of the rig is going through it. Don't over think why it blew when it did. Only the LandCruiser gods know.
so if I got the Bussman 150Amp rated one ... thoughts? because when car is on and everything bemused and then lets say I had to use my winch because was stuck (while those things are on -radio whatnot...the 50 would blow in a second...because just on the fuse block alone there at least 90amps being drawn. I have ARBlockers, aftermarket tach, dual solenoid (I hooked those up t can aux fuse box but its tied into my ignition therefore pulling from the battery all the same even though I did add a relay for that fuse box.

do you think 150Amp rated 12v Bussman is overkill? because I think that's what im gunna get considering im rebuilding my winch and want that connected with a quick disconnect so it doesn't cause any parasitic drain to my battery I have that already happening with my Red/clack interior light wire Iines..that particular fuse I have a out already after discovering that was main cause of parasitic drain
 
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I had a similar issue when the 15a engine fuse at the block would blow instantly when I turned the ignition.....it was the connections at the alternator, they were incorrect.

Did you try to unplug the alternator yet as mentioned earlier?
 
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I have my Hongda out and using it...so thank you...but to answer your Question ... no when I put fuse in is fine - I can turn on lights and honk horn etc..OBLy and ONLY upon turn of ignition does it blow.. how should I use my Hongda to diagnose?? meaning check what where..im sure if I sat and thought about it I would give myself my own answer, but its late and the last 4 days have been stressful to say the least.
so check continuity between the alt lines...volt at the ignition..volt at where then after that? I just dont know how to use it to narrow down whatever it is. walk me througusing the hongda correctly for this situation. help me learn for next time. thx

I haven't gone through your previous post with the details of your setup so this would is more just a general troubleshooting technique that I would use.

It sounds like there's a short somewhere on the ignition circuit. So a quick and easy way to start diagnosing it would be to start unplugging things until it stops. But blowing fuses will get expensive so that's where the continuity tests feature on the meter would help. First and foremost, test the meter and leads. While the meter is set for resistance or continuity reading, it's a good habit to touch the leads together to verify that the meter is working properly. With the leads connected, you should see a reading close to 0 (a few millohms is fine). With the leads disconnected, my meters usually show an 0L, or open.

I'd first start by disconnecting the fuse, then measure continuity between the vehicle side of the fuse and ground. With everything off you should see an open connection. When you turn on the ignition (but not starting) if you see the resistance dropping to near 0 then there's a short to ground somewhere. From there it's a matter of process of elimination, you can start unplugging or even wiggling wires (check any wires coming through the firewall or running near the engine), at some point it should go back to an open connection again. Again I don't know your particular setup so this is just a generic procedure.

so if I got the Bussman 150Amp rated one ... thoughts? because when car is on and everything bemused and then lets say I had to use my winch because was stuck (while those things are on -radio whatnot...the 50 would blow in a second...because just on the fuse block alone there at least 90amps being drawn. I have ARBlockers, aftermarket tach, dual solenoid (I hooked those up t can aux fuse box but its tied into my ignition therefore pulling from the battery all the same even though I did add a relay for that fuse box.

do you think 150Amp rated 12v Bussman is overkill? because I think that's what im gunna get considering im rebuilding my winch and want that connected with a quick disconnect so it doesn't cause any parasitic drain to my battery I have that already happening with my Red/clack interior light wire Iines..that particular fuse I have a out already after discovering that was main cause of parasitic drain

I don't think even a 150A breaker will work with a winch. Some winches pull 400+A under load. You can wire it through a large cutoff switch (flaming river or similar), but most people just wire directly to the battery. The solenoid pack or albright is your disconnect.
 
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I had a similar issue when the 15a engine fuse at the block would blow instantly when I turned the ignition.....it was the connections at the alternator, they were incorrect.

Did you try to unplug the alternator yet as mentioned earlier?

ya - I re-wried my entire power system area and I made TRIPLE SURE to get that all correct...It would have blown on startup originally if that was the case too - it wouldn't have driven fine for days and seat-ed up better than ever has since rewire
 
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I don't think even a 150A breaker will work with a winch. Some winches pull 400+A under load. You can wire it through a large cutoff switch (flaming river or similar), but most people just wire directly to the battery. The solenoid pack or albright is your disconnect.

ya so I apologize I think I was unclear on what I said but ya im directly connecting to battery via 2awg.....im curious about the bushman then in regards to jus the truck (nothing to do with truck vs winch) ... what size should I get considering I have dual fuel solenoid, stereo equipment, ARB lockers /switches, and aftermarket tach...bunch of little extra accessories pulling amps... I just want to make sure I buy the correct one...esp since im soooo novice in understanding electricity as it relates to cars and cable sizes/AWG's etc
 

workingdog

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So, it's not that critical (other than it not be too small). You're protecting the system from a catastrophic short and the alternator. All the individual circuits have their own fuses. All those things you listed don't draw that much power. I use a 50am. I think a 30amp might work. Not sure how much charge amperage the alternator could run through there.
 
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Side note, can be handy to keep a few lengths of wire with jumper clips on each end in the toolbag - pretty easy to jumper the coil (and the started) and bypass all the factory wiring to get it running and off the side of the road.

Similar to the bad starter thread and push starting...can be handy to get it going again, they're simple rigs.
 
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got it...so im way over thinking all the adding the amps together s***...ok just individually the winch protecting that and main line. got it so bushman 50a it is....thank you.

and then next quicky question: I'm replacing my main negative battery cable/lead to battery - should I go with 1 gauge?
 

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