IH 684 electrical issue

vezult

Member
I found that I couldn't start my tractor the other morning. After doing some investigation, I found that a fuse had blown. I replaced it, tried to start, and promptly blew it again.

Looking at the electrical diagram, it appears the the things on that circuit are (assuming I'm reading it correctly):

* keyswitch
* alternator warning light
* alternator
* safety start switch (bypassed, on my tractor)
* starter motor

I've attached the electrical schematic.

I'll admit that I'm a complete novice w/regard to electrical stuff. Any suggestions on debugging this?

Is there a likely culprit? Please don't say the starter :) I suppose I could just buy a replacement starter solenoid, and try that. That's definitely the cheapest thing to swap.
a242996.jpg
 
Each component should be disconnected from that circuit, a new fuse installed. If the fuse still blows with all disconnected, it is a short in the wiring and is harder to find looking for chafed and grounded wires. Then, starting with the alternator small wires, then the alt big wire, and so forth. Re-attach each component and test with the key. Jim
 
It blows in the start position, and I *think* it blows when I press the starter button. It sounded as if the starter was about to engage - maybe it was the click of the solenoid moving. That does make me think it might be the solenoid.

I didn't have enough fuses to do a lot of testing :)

Speaking of fuses...I googled "TDC 330-35A" which was stamped on the fuse. I'm not finding much. I've got one fuse left. Are these going to be hard to find?
 
Another way to approach this is to use an old headlamp bulb for a fuse. Temporarily wire it in in place of the fuse. If it glows bright without an assigned load, you have a short to ground. Then unhook likely suspected wires and watch the bulb. When it goes dim or out, you found the problem. Saves burning out any fuses, plus it's very easy to see when the problem is discovered. Also works great if you do have the aforementioned chafed wires. Just wiggle the wires in the suspected area and watch the bulb. You might even focus it on the ceiling or a wall, where you can easily see if the intensity changes.
Good luck!
 
I think the fuse you are using may not be an automotive type. The fuses I found with that number were milliamp and fractional amp fuses. The link below should help. Make sure the size is the same, and go for the amperage. A circuit diagram, or owners manual should be contacted to be sure of the amp rating. If the fuses you are using are fractional amp, they will blow if nothing is wrong. Jim
looking at them
 
It would be cheaper to buy the correct fuses-I can't tell from your diagram what amperage,but it may be on the holder on the tractor.I would bet 14 or 20 amp SFE. And it would be cheaper to use a multimeter,than to buy parts,and guess.Also look at the wire harness,follow it from the fuse to each component and check for chaffing-short to ground.Mark
 
I would check the switch and the solenoid. Both are prone to going bad. Is this a gas or diesel. As if a diesel listen for just the solenoid to click . If that is all it does then the solenoid is probably the culprit. Ih was notorious for poor wiring I always thought. I have replaced so much of it on tractors with real copper wire instead of that cheap steel wire they use.
 
I believe the manual says 35A. It may be that a lower amperage, slower acting fuse would do fine.

The manual doesn't specify SFE or AGC, but all the fuses are the same length, which according to my reading, makes me think they are likely AGC.
 
Well, I banged on the starter and the solenoid a bit, replaced the fuse with at 30A AGC fuse (couldn't find 35A), and the starter now works. It *does* seem as if something is getting awfully hot though, and even thought I saw some arcing at the terminal end of the solenoid as if there's a lot of resistance.

I think I may replace the solenoid anyway.

Thanks for all the advice, folks.
 

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