Alternator wire burning?

[Blueox4]

I have a 1958 861 Powermaster that I only plow snow with. It has had a 12v conversion for several years and this problem did not exist. Recently when I start the tractor the thicker red wire,which is one of three that are attached to the alternator, glows red hot and burns the insulation at where it’s attached to the alternator. It destroyed the connection for the red wire which is now hanging loose and not attached to the alternator. The tractor still starts with the red wire not attached to anything. Is it all right to run the tractor with only two wires connected to the alternator? What effect does not having the red wire hooked up? What’s causing this? Bad alternator?

 

[Bern]

You asked this same question last month, and I gave you the answer to your problem at that time (link below).

If you choose to leave the wire disconnected, your battery will eventually die. The wire in question is the main alternator output wire. Without it being connected, no charge output is going to the battery. None.
Jan 23 response

 

[Blueox4]

Thanks Bern but I didn’t get what you mean by clean it up. Do you mean clean the attaching nut on the alternator and are you saying that’s what’s causing this? Corrosion or bad connection there? Could it be the alternator itself? I’m just trying to understand this myself. Thanks!

 

[Jim.ME]

(quoted from post at 18:22:36 02/14/21) Thanks Bern but I didn t get what you mean by clean it up. Do you mean clean the attaching nut on the alternator and are you saying that s what s causing this? Corrosion or bad connection there? Could it be the alternator itself? I m just trying to understand this myself. Thanks!

He means it is dirty/corroded/burnt. It should be clean, shiny, bare metal on both, the stud and nuts of the alternator and the wire terminal as well. It is hard to tell in the picture, but blowing it up it looks like the battery/output terminal on the alternator is beyond salvage by cleaning. If that is the case, a replacement alternator is in order and I would put a new end terminal on the wire.

 

[Bern]

You can tell clearly in this pic that the connection is pretty rusty.
Rusty stud

 

[Bern]

Rust/corrosion/loose connections cause heat when current flows through it - in your case, enough heat to melt it. Put a new terminal on the wire (crimp it good and tight) and clean up the stud to nice bright shiny metal (and make sure the nuts are tight on both sides of the terminal) and you'll be good to go.

 

[MarkB_MI]

It's hard to say if the gnarly connection is the cause of the wire burning up or an effect. After you get everything cleaned up and reconnected, you need to do some tests with a voltmeter to see what's really going on. You may have a short inside the alternator (e.g. bad diode) that's causing the battery to backfeed the alternator. When running, the voltage at both the battery positive terminal and the alternator output should be around 14 volts. If it's less than 13 volts in either place or over 16 volts, something is wrong.

Running with the alternator output disconnected is probably not a good idea and might damage the alternator if it isn't bad already.

 

[Bern]

If the alternator was internally shorted to the extent that it would melt the terminal, the battery would be stone dead every morning.

 

[warbaby]

Yeah, I would refer to your earlier post.

If none of those answers ultimately solved the issue, I would seriously consider the amount of rust and corrosion that can be seen leaking out of the alternator itself (as shown in the original post) as an indicator of internal damage to the circuitry within the alternator.

 

[MarkB_MI]

> If the alternator was internally shorted to the extent that it would melt the terminal, the battery would be stone dead every morning.

True, unless he's in the habit of disconnecting his battery when the tractor's not in use. Which most folks don't.

 

[David G]

It looks to me like the connection has been bad or loose for some time, causing it to get hot and then rust. As stated, you need to clean the rust off so there is clean metal on the stud, put new end on wire and clamp it good.

 

[showcrop]

I recently had a similar situation with my snowmobile. To make a repair the seat had to come off and the battery is in the rear of the seat. The cables to the batteries are VERY TIGHT, and need to be persuaded to come far enough to be able to attach them. Soon after initial start-up I noticed insulation burning on a small ground wire at the battery. After considerable time trying to find the problem with the wire the problem came to mind. There was absolutely NO CORROSION involved, but when I tightened the terminal screw the heavy cable made a good connection but the small ring terminal, due to the stretch, never pulled down firmly onto the terminal despite the hold-down screw being very tight. Pulling some slack for the wire solved the problem. In adition to what Bern said to do, when a wire gets as bad as the one in the picture sometimes there will be considerable corrosion in the wire itself UNDER the insulation. Cut it back a little to check. You may need to cut off and replace a few inches.

 

[bc]

The insulation at the end of the wire looks expanded so Showcrop is probably right about some corrosion going back a little.

 

[warbaby]

Rain water running off the hood and onto the alternator will eventually cause it to fail- these rust stains are the tell-tale sign of water getting inside the case

 

[showcrop]

(quoted from post at 12:06:07 02/16/21) Rain water running off the hood and onto the alternator will eventually cause it to fail- these rust stains are the tell-tale sign of water getting inside the case
<img src="https://www.yesterdaystractors.com/cvphotos/cvphoto77865.jpg">

warbaby, I have never owned a car or truck with an alternator that has been inside the car. They have all been under the hood getting bathed in salt brine mist.

 

[warbaby]

Yes, but while they are spinning under that protective hood (the only time they will be exposed to that brine, unless youre towing it), they tend to shed the
debris thrown at them. An alternator thats just sitting out in the weather doesnt shed that water, it gets in it and starts causing problems.

But even under the hood they can get ruined- it depends on how low its mounted on the engine and how deep the creek is your "friends" talked you into fording!

 

[Bern]

Interesting observation, however that rusty nut did not come about because of what was going on inside the case. There's an insulating sleeve between the stud and the case that would prevent that. The rust in question happened because the terminal got red hot.