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TO20 Alternator White Wire Hot


 
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zparnell
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PostPosted: Sun Nov 22, 2020 2:47 pm    Post subject: TO20 Alternator White Wire Hot Reply to specific post Reply with quote

I have a TO20 with a 12v conversion. It has never charged since I bought the tractor. Over the past two weeks Ive been working on that problem. I have connected the wiring up according to diagrams I found on here and other places. I have an amp meter and a voltmeter on it now and I have noticed it reading 13.7 V to 14.1 when running so it appears to be charging. However today while running the tractor I started to smell hot wires. The white wire coming from the alternator to the accessory position only key switch was hard to the point of melting so I disconnected it. What could be going on here?
 
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pomester
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PostPosted: Sun Nov 22, 2020 6:55 pm    Post subject: Re: TO20 Alternator White Wire Hot Reply to specific post Reply with quote

"The white wire coming from the alternator to the accessory position only key switch was hard to the point of melting "

Is this a 'one wire' alternator with an internal regulator? I don't think there should be any wire running directly from the alternator to the accessory terminal of the key switch. Current coming into the key switch should come in the main (usually center terminal) and then the accessory terminal goes out to lights or whatever accessory you might be running.
 
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zparnell
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PostPosted: Sun Nov 22, 2020 8:05 pm    Post subject: Re: TO20 Alternator White Wire Hot Reply to specific post Reply with quote


that should say "hot" to the point of melting. I could not edit it.
1 wire coming from the tap to the ammeter, switch, and resistor, and the 2 spade plug, one going back to the main tap and the white wire going to the accessory term on the ignition switch. That was my interpretation of the instructions.
 
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pomester
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PostPosted: Sun Nov 22, 2020 9:14 pm    Post subject: Re: TO20 Alternator White Wire Hot Reply to specific post Reply with quote

"1 wire coming from the tap..."

what is the 'tap'? The + terminal of the battery?

The power from the alternator should be a #10 wire, should run to a terminal of your ammeter, then from the other terminal of the ammeter to the battery. Volt meters and key switches should draw power somewhere after the ammeter and not be part of the charging circuit. The output of the alternator should not run thru the key switch.

Your tractor originally came with a 3 wire generator with a separately mounted voltage regulator. It's had to been rewired to accommodate the alternator and there are different acceptable ways to physically configure the system.

I'm sure your word picture is clear in your mind, but I'm uncertain if I am understanding it correctly.
 
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Steve@Advance
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PostPosted: Mon Nov 23, 2020 4:15 am    Post subject: Re: TO20 Alternator White Wire Hot Reply to specific post Reply with quote

Sounds like it is charging through the ignition switch.

What terminal of the alternator is the white wire connected to?
 
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zparnell
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PostPosted: Mon Nov 23, 2020 4:23 am    Post subject: Re: TO20 Alternator White Wire Hot Reply to specific post Reply with quote


Yes, the "tap" as I called it is the charging wire coming from the main lug of the alternator to the ammeter on a #10 wire as you described. There is a 2 prong plug on the side of the alternator, it has a #10 red wire on it and a small #14 or 16 white wire. When I got the tractor the plug #10 wire was going to the battery and the charging wire was connected to the solenoid. Ammeter was bypassed. I'm not sure where the small white wire went. There was no charging happening. I have since run the plug #10 back to the charging lug of the alternator to excite charging and the white wire I put on the accessory connection of the switch as in a diagram I found online. That is obviously wrong in my situation.
Do I not need to worry about the wires from the plug and just leave them unconnected?
Thanks for trying to understand my confusing connections.


 
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Steve@Advance
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PostPosted: Mon Nov 23, 2020 5:50 am    Post subject: Re: TO20 Alternator White Wire Hot Reply to specific post Reply with quote

The white wire needs to be moved to the #1 terminal on the alternator. That is not exactly right, but it will work. Just be careful not to leave the switch in acc, it will run the battery down.

Then run a 10 gauge wire from the BAT stud on back of the alternator to the amp meter. One side of the amp meter wires to the battery, everything else, including the 10 ga wire from the alternator, goes to the other terminal. If it reads backward, reverse the wires.

Leave the jumper from the BAT stud to the #2 as it is.

It really needs the harness connector that plugs into the side of the alternator. It will keep the wires from falling off or shorting to the case. You can get it at any auto supply in the electrical section.
 
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zparnell
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PostPosted: Mon Nov 23, 2020 6:13 am    Post subject: Re: TO20 Alternator White Wire Hot Reply to specific post Reply with quote

The harness connector is there and has the small white wire on it. The red wire was on there also but when it got hot, the red wire spade connector pulled out when i tried to remove the connector. The # 10 white looking wire in the picture is really a red wire badly faded. It currently does go to the ammeter. The small white wire was run to the acc on the switch and that's what was getting hot. Should I just leave it off or does it connect somewhere else??
 
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Steve@Advance
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PostPosted: Mon Nov 23, 2020 8:01 am    Post subject: Re: TO20 Alternator White Wire Hot Reply to specific post Reply with quote

Sounds like it was wired correctly then.

Wonder if something has failed internally of the alternator.

The wire from the ignition switch to #1 is supposed to have a resistor or diode in it. Commonly a small incandescent lamp is used as a resistor. You might try adding the resistor, and at the same time take the alternator in and have it tested. Possibly the diode trio has failed. You can either replace the diode or exchange the alternator if it tests bad.

The resistor doesn't have to be a visible light. You can just put it in the line and tape it up out of sight.
Lamp Socket Used as a Resistor

 
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zparnell
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PostPosted: Mon Nov 23, 2020 8:23 am    Post subject: Re: TO20 Alternator White Wire Hot Reply to specific post Reply with quote

I already have a resistor inline with it. I have not checked it with a meter yet. Taking the alternator to be checked might be in order.
 
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rvirgil_KS
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PostPosted: Mon Nov 23, 2020 1:12 pm    Post subject: Re: TO20 Alternator White Wire Hot Reply to specific post Reply with quote

Steve has you covered on the wiring connections. I would definitely get a new 2 pin plug.

The #1 pin requires only a momentary voltage at start up to get the alternator charging, then the internal diode trio takes over and supplies power to operate the regulator. #2 pin is battery voltage sensing to tell alternator how much to charge.

When switch is turned on there is 12 volts at #1 pin connection at ACC on the switch, and depending on isolation device a lesser voltage at #1 pin on alternator. When alternator starts charging the diode trio supplies near battery voltage internally to #1 pin. With battery voltage on both ends of the wire there is only minimal current flow through it. If the wire is getting hot something is causing excess current flow through the wire.

An accessory tap on the switch sounds like a non-original switch, but if working properly is ok.

The purpose of diode, resistor, or lamp in #1 line is to prevent alternator feed back through the switch to coil allowing tractor to continue to run when switch is turned off. The accessory pin on the switch should be isolated from ignition pin when switch is off so the isolating device is actually not needed with the accessory switch. However it does add protection from an alternate charging route through the lighter gauge wires if the 10 gauge wire from alternator output to ammeter were to fail.

I would look for shorted wire or defective alternator causing the wire to overheat.

Alternator output and all switch supplies connect to one side of ammeter, other side of ammeter goes to battery connection at starter switch device.
 
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