All sudden a fuse blows question

[SleepyFarmall]

Been running a brush hog over some tough ground, when after about a day, the 5-amp ignition fuse blew. Had a spare, so back in business for about 20 minutes then that one blew. Replaced that fuse 9 times and made it back home on my last spare. I've looked and looked for bare wire and found nothing. Replaced the ignition switch also with no change in symptoms. I'm at a loss. I'll check the book to see what all is being powered by that fuse and maybe it'll give me a clue. Can a alternator be shorting out internally and causing this? Can the PTO have something to do with it?

Just wondering if ya'll have a suggestion.

It's a New Holland TC30 with 730 hours
Thanks for any help, Michael

 

[Geo-TH,In]

Just wondering if ya'll have a suggestion.

My suggestion is to buy a cheapie clamp-on DC ammeter to find the problem.

Fuses blow because of excessive current or excessive temperatures. A bad fuse holder will get hot and blow fuses. An IR thermometer can tell you which wire or if the fuse holder is hot.

Amazon sells this cheapie meter for around $30.
I'm impressed with its accuracy.

Or you could use a 30 amp fuse and wait for something to get hot. It will let the smoke out of the wire. A good idea to carry wire cutters and a fire extinguisher if you use a 30 amp fuse.

 

[r.w.b.]

i second hf tester , plus they stepped their game up n got several items that perform flawlessly for less.
back to tractor im thinking mice coulda got in wires n chowed on a wire,the bouncing might made it bump into a direct ground.and cold even be the alt cause new fuse n run a bit.
best of luck finding wiring problems are not always easy.
to share with you i left in rain yesterday in the older kenworth t 600 pulling newest timpte trailer full of corn. last year lights on middle of trailer to front went out.new relay box cured it. yesterday same thing but relay didnt help this time. se we both got a problem with wiring

 

[Janicholson]

You know it was more than 5 amps, but not much more. You know it is consistent. The fuse blows because of 2 things heat from a cruddy fuse holder, or overload. putting in multiple fuses would have/did burnish the fuse holder contacts and let it be OK. I would look at the wiring to see if more than the coil was in the circuit. If so then there are multiple potential draws. If not, the coil might be going bad. they can increase the amps through them if they have an internal short between windings. This causes the windings to appear lower in resistance. If you are electrically capable, measuring amps is easy with a modest cost meter. it needss to be placed in series with the circuit you are testing. The one Geo is indicating is a good resource, or less expensive.
The coil should measure about 1.5 ohms if it is in a resistor circuit, or 3 ohms if it has no resistor (less likely) If it reads less than 1 ohm, it is likely the problem. Jim
Harbor Freight

 

[olddavid]

Just a thought. Fuses will occasionally blow for no apparent reason. Too many high current spikes or cycles or whatever. Did you put the same value fuse in? Obvious, I know. Next, was the one you took out a slow-blow fuse and did you put a slow-blow fuse back in? Most will say it on the fuse but Little Fuse will have a different number for the type. Amps ain't necessarily just amps when it comes to fuses. Having said all that, bare wires are sometimes a bear to find and it may still be that.

 

[flying belgian]

How about disconnect that wire on both ends and run a jumper wire. If that works you know the problem is bare wire and you will have to look harder.

 

[ken44520978]

My favorite way to work on intermittent short circuits is to replace the fuse with a light bulb. If the circuit is protected with a 5 amp fuse it probably passes 2 amps maximum. I suggest placing a sealed beam headlamp across the fuse holder. When a short occurs the lamp will be bright. When no short the tractor will most likely run fine. You can move wires around and watch for the lamp to blink on.

 

[DoubleO7]

(reply to post at 08:31:40 09/23/23)

Look at all the places the wiring passes thru sheet metal.
Maybe the grommet has worn or split allowing a wire to rub the steel. Usually at the bottom edge of hole.

 

[cuby]

Take grd off bat. Hook test light between cable and bat terminal, trace wires, light goes out there is your short or if light comes on same difference. Just my way.

 

[SleepyFarmall]

As luck would have it, I just received that very meter in the mail today. I hear it is much recommended. Maybe someday I'll be smart enough to use it. Michael

 

[SleepyFarmall]

When I drove truck, ABS light on trailer was a problem. Never figured out why any of them wouldn't extinguish, just reported it. Michael

 

[SleepyFarmall]

That sounds like a good idea. I'll try that next. Michael

 

[SleepyFarmall]

Today, I cleaned as many connectors as I could find, including the fuse block. Ran it for a while idling and checked with my IR thermometer and found nothing of note. But it didn't shut down. So, maybe I got lucky. I can't see any wires compromised after much looking. I'll know when I go back to mowing after this rain stops. Thanks, Michael

 

[Geo-TH,In]

The meter is simple to use.
Set the meter to measure DC amps and clamp it on the power wire with the fuse. It will tell you the amps going through the fuse.

Post back with the amps it's showing.
Keep in mind a fuse protects the wire from catching on fire.

I question if a 5 amp fuse is large enough for your load. What is the load in the circuit?

What is your wire size?

This meter might be overwhelming for the electrically challenged. You can always learn.

 

[SleepyFarmall]

I'll check with the meter tomorrow.

More details:
-my documentation says it's supposed to be 5 amp fuse.
-at one point I ran out of 5a fuses and used a 10a; it also blew after about an hour.
-I'm unconvinced the problem is fixed; there has to be a intermittent dead short but it is not exactly random; kinda predictable like every 20 minutes
-the circuit supposed to power Safety controller, park brake switch but the manual may not apply to my tractor; its a little vague. I didn't even know there was a park brake switch.
-It's a diesel; 2007 year
-if its a component failure I was hoping someone could say they had the same issue and what resolved it.

Thanks for your input, Michael

 

[BarnyardEngineering]

When the fuse blows the engine shuts down, or?

If the engine shuts down the fuse is ultimately powering the fuel shutoff solenoid on the injection pump. #23 in the diagram:

https://www.mycnhistore.com/us/en/n...56875BD6/780EAD4F-E6BE-E111-9FCE-005056875BD6