M9960 Charging system

[Eutychus2]

The used 9960 bought in June 2024 was used all summer. The battery was new, i.e. March 24. I found that the battery would be depleted in about 2 days, so after finishing up for day at work site, drove it to garage and hooked it up to a charger. The checker dash gave no indication of a charging problem except when going down the highway at high RPMs of around 3000 at which time the battery light would illuminate ( so I slowed it down). Now that it started raining and too wet to work, I started looking for the problem. Following the WSM alternator tests I found the 60A slow-blow fuse inline to the battery + is burned out. I have not attempted other alternator tests from the WSM. I did check that the wire on both sides of the fuse is not shorted to ground.

An attempt to get suggestions from my Kubota dealership as to what could cause the fuse to blow or to even to speak to a mechanic about it was rebuffed. "I need to have them diagnose it."

Your suggestions would be appreciated. I have the fuse but would hate to install it and have it immediately blown.

 

[Edke6bnl]

no ace here but I would put the fuse in and check the voltage at the battery and if you can put a clamp on amp meter to check the amps out. fuse blown could be as simple as a bat connection at fuse block and high draw.

 

[Eutychus2]

I do not understand about the bad connection at fuse block and high draw. I am attaching the electrical diagram. The alternator is 45A according to the WSM. So, I think I would have to get a new tester since mine does up to 10A.

 

[GreensvilleJay]

Based on your post... new battery in March, ,sold to you in June....
It's possible the previous owner blew the fuse when changing battery then just 'topped up' the battery when he used it....

It's possible the alternator is 'bad', though check the fan belt !! A slightly less than snug belt won't allow battery to be charged, properly.

Replace the fuse... and measure the battery voltage (say it's 12 )
Now start engine and read battery voltage (say it's 14 )
This should indicate alternator is OK....

Agree ,putting ammeter in series with 60A fuse is the best test,but most DMM don't have high current option.

 

[Eutychus2]

I got the tractor at auction so I was thinking the previous owner knew there was some problem with the charging or battery (at least) and simply put a new battery on it so it would start.

I did not mention that I had checked the fan belt because the battery will not charge with a blown fuse according to the electrical diagram. I am told that some parts stores check alternators for serviceability. I am considering that.

I have considered replacing the fuse and trying it. However, the only reason I started this thread was to try to avoid doing that and possibly blowing out the replacement.

 

[PoTreeBoy]

I got the tractor at auction so I was thinking the previous owner knew there was some problem with the charging or battery (at least) and simply put a new battery on it so it would start.

I did not mention that I had checked the fan belt because the battery will not charge with a blown fuse according to the electrical diagram. I am told that some parts stores check alternators for serviceability. I am considering that.

I have considered replacing the fuse and trying it. However, the only reason I started this thread was to try to avoid doing that and possibly blowing out the replacement.

I'm not a fan of repetitively blowing fuses, but you haven't even blown one yet. Look for bare wires, put it in and try it. Use a 40 or 45A if you want. If it blows, try to see any other sparking areas.

 

[Eutychus2]

The only reasons for a blown fuse are a direct short in the circuit or can the 45A alternator somehow put out more than 60 amps? Or what?

 

[Eutychus2]

I'm not a fan of repetitively blowing fuses, but you haven't even blown one yet. Look for bare wires, put it in and try it. Use a 40 or 45A if you want. If it blows, try to see any other sparking areas.

Kubota is selling these fuses for $29.76.

 

[PoTreeBoy]

Kubota is selling these fuses for $29.76.

Yeah, but you're driving a Kubota now ! Seriously, they should be available substantially cheaper at Advance, AutoZ. . . Buy 2, that way you'll have one you never need.

 

[GreensvilleJay]

OK, you can start and run the engine...
with a fully charged battery, insert a 30-40 amp fuse if you have one. it probably won't blow as battery has only been used for 30-60 seconds. and will not require 30 amps let alone 60

 

[North Idaho Wolfman]

Go to a auto parts store and pick up the largest Circuit breaker of this style that you can get it doesn't really matter is it's 30, 40, 50, 60...
Add a couple leads and plug it into where the fuse goes, you do not need to mount it.
If it snaps (trips) instantly you have a shorted diode trio in the alternator and it will need rebuild or replaced.

Hang onto it for future test needs, as it resets once cooled down in about 10 seconds.

 

[Eutychus2]

Yeah, but you're driving a Kubota now ! Seriously, they should be available substantially cheaper at Advance, AutoZ. . . Buy 2, that way you'll have one you never need.

And if/when you do need it, you won't be able to find it.

 

[Eutychus2]

Update: I had the alternator tested and came back good. I put in 60A slow blow fuse and checked for continuity and shorting. Everything seems to be fine and battery is being recharged. As some one said (I think), the previous owner must have shorted something out when putting in a battery or other work and caused the fuse to blow. I also learned that a 45A alternator can put out more than 45A when its RPMs are above the RPMs for which the alternator is rated for at 45A.