Farmall SH 12v - Killing batteries

Hey guys! To start out, this tractor was converter to 12v when I bought it, but the wiring was a mess! Bought a Brillman harness and installed it. Next day, battery was dead so I charged it and didn't think much of it. Seems like every tractor I buy needs a battery anyway! Lol. Come back out a couple days later and battery is dead again. So back on the charger it goes only.nkw it won't take a charge so I need a new battery. Checked all the wiring and discovered I had switched the wires going into the alternator (Mitsubishi). So I corrected that and installed a new battery. Unfortunately the new battery lasted about 3 weeks and now it's dead and won't take a charge! I thought I had all the wiring correct...maybe it's the alternator? Any thoughts?

Wiring looks correct to me, although I am going to change the power wire to the light switch, to the other side of the ignition switch so lights can't be turned on while tractor is off.
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Where does other end of black_white wire on L terminal on alternator connect? It should go through a diode, resistor, or idiot light to output of ignition switch.

I personally would not change the light switch wire. Not knowing the current capability of the ignition switch I would not want lights current to go through the switch. Also, there may be a time you would desire the lights to be on with engine not running.
 
Your alternator is taking a tiny bit of juice all the time it sits not running trying to energize itself to make electricity, that's why it needs the diode, an electrical one-way check valve. OR, what I did was put a quick disconnect on the battery ground cable so the entire electrical system is dead, no parasitic drain on the battery, takes two seconds to connect the ground cable and my last Die Hard Gold group 65 battery lasted 20 (TWENTY) YEARS in my stage II Super H.

Not sure how old the battery in the M is but it's the one that was in it eleven years ago. Both tractors have Delco 10si alternators.
 
I would have to double check the Brillman harness but I believe it is spliced into the black wire with white tracers that goes to the coil.

I have converted a few tractors over to 12v before and have never had the need for the idiot light or diode. Wonder why? What are you guys using for your light or diode?

Thanks for the help!
 
"I would have to double check the Brillman harness but I believe it is spliced into the black wire with white tracers that goes to the coil" That would be electrically the same as going to the switch.

If harness was made for alternator it may have diode built into the harness.

The L connection on your alternator (same as #1 on Delco)needs a voltage at start up to start the alternator to charging. If there is no isolation in that line, power from the diode trio in the alternator can feed back to the ignition system preventing the engine from shutting down when the switch is turned off. Purpose of diode, light or resistor is to prevent backfeed and allow engine to shut down when switch is turned off.
 
That's not the wire got the coil. IF it has a diode in it, it comes from the L terminal on the alt. I wire mine n on a oil pressure switch, that's Teed into the oil line to the gauge.
 
"rvirgil_KS" hast RIGHT... "The L connection on your alternator (same as #1 on Delco)needs a voltage at start up to start the alternator to charging. If there is no isolation in that line, power from the diode trio in the alternator can feed back to the ignition system preventing the engine from shutting down when the switch is turned off. <strong>Purpose of diode, light or resistor is to prevent backfeed and allow engine to shut down when switch is turned off."</strong>

That's CORRECT... that's when the diode comes into play.

On the other hand, "John M" and "DR. EVIL" have it WRONG... once the engine is shut down a diode, lamp or resistor in the "excite" circuit to the #1 terminal will have NO EFFECT on whether or not the battery drains.
 
never had the need for the idiot light or diode

Three possibilities:

1. You use/used the tractors frequently enough that the alternator did not have time to discharge the battery.
2. You wired up manual excite circuits for the alternators, a toggle switch or a push button.
3. You used one wire alternators.
 
(quoted from post at 06:35:45 04/27/17)
never had the need for the idiot light or diode

Three possibilities:

1. You use/used the tractors frequently enough that the alternator did not have time to discharge the battery.
2. You wired up manual excite circuits for the alternators, a toggle switch or a push button.
3. You used one wire alternators.

B.E.... Just to clarify... So you are of the opinion a diode, "idiot light", or resistor in the excite circuit DOES prevent battery discharge after shutdown, contrary to what "rvirgil_KS" and I have posted?
 
Bob, if I'm understanding your post correctly, adding a diode, "idiot light", or resistor is to prevent back feeding FROM the alternator. That is currently not an issue I'm having...alternator charges just fine and tractor shuts down as it should. So, if the suggested diode, "idiot light", or resistor are installed for that reason, what do I need to do to fix my issue of draining the battery?
 
There is one black wire with white tracers going from the ignition switch and into the harness. Above the valve cover, there are two black wires with white tracers coming out; one goes to the alternator and one goes to the coil.
 
That's what I'm not sure about either. The harness was made for a 10SI alternator and I had to change plugs. I had the wires switched initially, when it drained the battery the first time, I thought I had them wrong so changed them to how you see them now.
 
Not what I said, I just said he needed it, but since I dont see it mentioned there was a problem with it shutting down, it may well not be needed.
 
(quoted from post at 08:13:51 04/27/17) Not what I said, I just said he needed it, but since I dont see it mentioned there was a problem with it shutting down, it may well not be needed.

John M, I fully agree with you, there needs to be a diode, resistor, or "idiot light" in the "excite" circuit to ensure that the engine doesn't "run on", and to protect the alternator.

HOWEVER, adding a diode WILL NOT cure the "battery going dead" issue.
 
(quoted from post at 07:36:03 04/27/17) Bob, if I'm understanding your post correctly, adding a diode, "idiot light", or resistor is to prevent back feeding FROM the alternator. That is currently not an issue I'm having...alternator charges just fine and tractor shuts down as it should. So, if the suggested diode, "idiot light", or resistor are installed for that reason, what do I need to do to fix my issue of draining the battery?

First, check the voltages at the "L" and "S" terminals with the ignition "off", and the 2-tab connector plugged in.

Then, unplug the connector, and record the voltages at both terminals in the plug and both "tabs" in the alternator and post back.
 
Yes

On this Mitsubishi and Hitachi "L" terminal is for charge indicator "Light". Other should be marked "S" for Sense. It senses battery charge level

L = #1 and S = #2 terminal on Delco

Since this replacement harness was made for an alternator configuration it may have a diode installed in the wire from S terminal to junction with coil wire. Diode would affect only the alternator, not the coil.

An ohm meter check between L and coil or switch would solve the mystery. Disconnect plug from L terminal on alternator and measure resistance to coil input. Then reverse meter leads and compare the two readings. Very low and near equal resistance both ways indicate no diode. Significantly higher resistance one way and lower resistance opposite way = diode is installed.
 

Its not a more/ less resistance thing with a diode, its a forward voltage drop and continuity one direction, and no conduction the other direction ( at least till you over on the peak inverse voltage anyway ).
 

Why would the voltage sense wire have a diode and go to the coil?

Sense wire theoretically should go to the battery to measure voltage drop from charge stud to bat post, and up the voltage accordingly, so you get proper charge voltage at the battery.

You go adding in series resistance or forward voltage drop in the sense line, and the alt will overcharge! Because it thinks the potential at the battery is lower than the charge output. The difference will be the voltage drop across that series resistance, or the value of the diodes forward voltage drop.
 
"Since this replacement harness was made for an alternator configuration it may have a diode installed in the wire from S terminal to junction with coil wire. Diode would affect only the alternator, not the coil."

Oops...74 year old eyes, brain and fingers not in sync......should have read "L" terminal Guess I get 3 lashes with a wet noodle
 
It all sounds complicated!
If it were my machine I would get out a good multimeter / ammeter and check that there is not a discharge from the battery when the tractor is switched off. You can disconnect a terminal and connect your ammeter from battery post to wire terminal. If you are not using a charge/discharge ammeter, be sure to wire it the right way around!
If the needle moves, the battery is discharging while the tractor is switched off. If not, then you may have:
a). poor connections somewhere
b). defective alternator
c). defective battery
If the ammeter shows a large discharge, you may have a dead short. This is unlikely, because by now, it would probably have burnt out the wiring if this were the case.
SadFarmall
 

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