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1981 444 with K321 Burning 20amp fuse after 2-3 starts

1926 Views 7 Replies 4 Participants Last post by  Hydriv
My recent addition 444 is burning the fuse running between the switch and ammeter. Engine starts up, tractor runs fine, but after a couple of start cycles, the fuse burns out. The prior owner bypassed the ammeter so I reconnected the leads (pain to get to) and the problem continues. The ammeter guage shows 10 amps +- when running. I am using an automotive 20 amp fuse as this is what I believe the specs call for and don't want to go higher. Have checked the wiring diagram and everything seems to check out. Anyone run into this? Power surge? Wrong fuse? regulator?Wrong switch? (the starter swich in the tractor looks fairly new but is unlike the ones on my 446 and 448 in that it has 5 prongs (1 unused) vs. the 4 on those? I tracked/matched the codes on the current switch and everything matches up--the tractor starts and runs fine.


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Not positive but I think the fuse should be 30 amps.....but there could be a reason the 20 amp is blowing so quickly. Any shorts that you could find?
No shorts that I could find. It seems to occur when the motor is running and the system is putting out amperage. Could be that it needs a 30 amp fuse. I will review the specs because I seem to recall the parts list calling for a 20 amp fuse, but the ammeter gauge says 30 amps. I wanted to stay conservative because it's cheaper to replace a fuse than burn out wiring : ). I also notice that the amperage meter on this tractor when running seems to run higher than my others--not necessarily a bad thing--but more than on my 446.
Your ammeter should not show 10 amps all the time. I would want to conduct two tests on that battery. The first test would be with a hydrometer to see if the state of charge in all six cells is identical or not. I would then subject it to a load test to see what that shows.

What is the serial number for your 444? I question whether your tractor came with a 5 prong ignition switch. All too often, owners go and buy an aftermarket switch and base their decision on the number of prongs it has and think that all switches are are constructed the same internally. Using only an OEM switch is the way to go.

That's where I would start. If the switch is not correct for your tractor, then you would be wise to purchase the correct one from Brian. Use you serial number to see if we have your Operator's Manual. If so, then the correct fuse amperage will be shown there. Case used 20 amp fuses in some models and 30 amp in others. Restoring the electrical system back to OEM specs should be the first order of business. Diagnosis becomes a lot simpler then because you have purged the tractor of all the voodoo caused be previous owners or repair people.
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Thanks for your responses. The serial number is 11074885--shows as a 1981. I thought I downloaded the proper manual but will double check. As it happens, I have another new battery and will swap them out. I am sure this is not the original switch--at least I have never seen one like it on my two others. I forgot to mention that in my "trouble shooting" today I examined the switch and found no "lights-on" detent position on this switch-so it's gotta go anyway. As it happens, I have a couple of spare used ones lying around so will swap that out and see if that makes a difference. You are so right on the "all original" suggestion...among other things, a previous owner, instead of simply replacing the choke cable, installed an off-the-shelf cheapo. Of course, makinig a nice 3/8 inch hole in the panel. :headscratcher: That's gone.
I just checked the parts manual for your model 444 and it shows a 20 Amp fuse. You may have a regulator problem or a battery that is in poor condition and demanding the max from the charging system. The new upgraded regulator is P/N C31249. But I recommend that you inspect the electrical system particularly where there are connector plugs. Look at the rear of the key switch to see if there is any melting of the plastic connector plug. I have cut off many of these connector plugs and crimped on new slip on connectors and reconnected them to the key switch. Bear in mind that all the electricity flow on the tractor goes thru the key switch except for the high amperage part of the starting circuit.
I have also removed the connectors on the charging systems on several tractors and crimped in butt connectors. In time all slip together connections will get corrosion and cause high resistance to the flow of electricity. I have had to disconnect and clean all the slip together connections that are not easily replacable on my 1990 4018.
Bob MacGregor in CT
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I finally got around to looking at this again today. I replaced the new aftermarket switch put in by the previous owner with an old spare I had on hand and voila, I have been through 8 start cycles without a hitch and the ammeter works fine.
That is a very common mistake made by owners. They think that they can just go and buy any ignition switch for these tractors but in truth, they cannot. You must use an OEM switch or you will have some sort of problem to deal with.
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