30A Slow Blow Fuse Blowing While Turning off Engine

[greggeorge13]

I own a Kubota 2320 and I keep blowing the 30A slow blow fuse when turning the engine off. It seems to happen after I operate the tractor for awhile and then blows the second I turn the ignition switch. I've replaced the Regulator for $140 but that didn't solve the issue. At $10 per fuse I hope I can solve the problem soon.

Do you think I need a new ignition switch?

 

[North Idaho Wolfman]

Yea it sounds like a switch issue, most are case grounded so if it's shorting to the case that will do it.

Get a manually resettable circuit breaker to use inplace of the fuse till you get the issue sorted out.

 

[BruceP]

Intermittent electrical issues are the most difficult to isolate and resolve.

Here is how I would troubleshoot such an issue:

1) Wire in a CURRENT METER where the slo-blo fuse goes. (No more paying for fuses for now) This meter needs to be able to perform PEAK_HOLD so it can capture the occurrence.
2) Without starting engine, turn the key back and forth between "run" and "off" many times while monitoring the meter. Try to capture when the current-spike happens.
2b) If you cannot capture it, you may have to repeatedly start/shutoff the engine to capture it.
3) Once you can repeat the issue... start disconnecting things (regulator, glowplugs, etc) one at a time until the problem goes away.
4) Once you have isolated to problem-circuit... it is trivial to troubleshoot from there.

NOTE: It is also possible to use a properly-sized lightbulb(s) inplace of the fuse to perform the above. The bulb will only light when excessive current is drawn. The reason this works is becasue a lightrbulb is LOW resistance most of the time and will still act a protect the circuit if excessive current passes thru it.

BTW: This is known in the electrical world as a "dim bulb" test. (I always save old headlight bulbs to use for dim-bulb testing...just solder a couple wires to it with some clips on the end.) In this way, I can mix-n-match the number of bulbs I need to put in parallel to properly-size to the load.

 

[ADKer]

BruceP,
I’ve got a BX2680 that’s basically dead in the water, as they say. Absolutely nothing when you turn the key. Did a little troubleshooting and found a blown 50A slow burn fuse. A reasonably new machine with 175 hrs had been running without any issues, mowing, brush hogging, and snow blowing (a very busy Winter in Upstate NY!). Anyway I was using the bucket, turned the machine off and when I attempted to restart nada.

in your post you talk about attaching a bulb to the fuse socket so that you’ll get visible continuity status: ie if the bulb lights up you have a short present.
If I used a bulb socket and attached some flat connectors and put a 12V bulb in it would that work as I checked for loose/frayed wire on each of the circuits that are fed by the slow burn fuse?

Hope I’m making sense; have limited electrical experience.

 

[chim]

The bulb makes more sense than a current meter if you suspect a short. That is unless your meter has some very high amp capabilities. Most consumer grade inline ammeters wouldn't be very happy with the current it takes to blow a 50A fuse.

You need to know what kind of load might normally be expected. A large (normal) load might illuminate a bulb to approx. full brightness. Back in the day we used incandescent light bulbs to temporarily replace Edison base fuses while checking for shorts.

Oh, and any electrical glitch is called a "dead short" by non-electrichickens

 

[ADKer]

I’ve got a Klein MM320 that has a 10A limit I think. Cranking the tractor contributes to the 50A load so we’ll test with just the key on not cranking. Would the bulb have to be 12V vs a normal house voltage one? If the short is caused by a faulty component like a starter, by disconnecting it the light should go out right?
Thanks for feedback BTW!