John Deere 40 Has Short Draining Battery After 12V Conver...

JdubyaM · Mar 23, 2014

Hello,Can anyone tell me the best way to trouble shoot my 1954 John Deere 40 for a dead short draining the battery. It has a 3-wire alternator. When I take the positive hot cable off the battery and hold it close to the post, it arcs. Thanks JW

Anonymous-0 · Mar 23, 2014

Never disconnect an alternator from the battery, when the tractor is running, chances are you blew the diode cluster when you did that...

Richard G. · Mar 23, 2014

Put a master cut off switch on a battery cable. Stops the problem and prevents fires from old wiring.
Best thing I ever did.
Richard in NW SC

JdubyaM · Mar 23, 2014

Thanks for your follow up. I didn't take the cable off the alternator. I took the hot wire off the battery post and rubbed it close to the battery post and it arced.

JdubyaM · Mar 23, 2014

Thanks Richard. Do they sell those at local parts stores? JW

David G · Mar 23, 2014

A cutoff switch is not for troubleshooting. No need to use one if it is working correctly.

JdubyaM · Mar 23, 2014

Also Richard, I am concerned with the wiring have a dead short and catching on fire and burning the wires off when I am running it.

IH2444 · Mar 23, 2014

(quoted from post at 21:05:56 03/23/14) Thanks for your follow up. I didn't take the cable off the alternator. I took the hot wire off the battery post and rubbed it close to the battery post and it arced.

Same thing if the engine is running.

If the engine not running, another thing altogether.

JdubyaM · Mar 23, 2014

Thanks David. Yeah... I really need to get to the root of the problem. There is something shorting out on the wiring, switches, or ammeter , alternator, starter etc. I have a test light and a meter but I am not experienced on using them. Thought someone might have some tips and even a 12V conversion wiring diagram to ensure the wiring is correct. I just bought the tractor and the previous owner converted it to 12V. I just bought a new battery too.

nebken · Mar 23, 2014

three wire system. The stud on the back should connect to the amp meter.

Where are the other two wires connected?

I'm guessing the wire connected to the switch is the problem. it must have a diode in line.

Unplug the two wires and see if you still have a short.

JdubyaM · Mar 23, 2014

Thanks NebKen. The large no. 10 ga. wire connects from the Alt to Starter Switch. The smaller 12ga. on the left top of alt connects to the tractor switch. The other smaller 12 ga wire connects to the starter switch as well. I will disconnect them tomorrow to see if the short still exists.

buickanddeere · Mar 23, 2014

A dead short can cause a fire.Is it a dead short?
Did somebody reverse polarity and short the diodes?
If it's a trickle discharge the excitation wire wasn't connected properly.

Many of these 12V "improvements" end in fires, shorts or tractors that only get charged from a 120V charger.
Nothing wrong with the factory 6V system on these small engines.

JdubyaM · Mar 23, 2014

Thanks buickanddeere. I think it has a short because when I take the positive battery cable off and hold it near the positive post, it arcs pretty good. Pretty strong arc. I am not sure what the previous owner did to it. I just bought it and put a new battery in it and the battery died overnight so I started checking and found the battery being drained by something in the electrical system.
JW in Georgia

Bob M · Mar 23, 2014

Disconnect the heavy wire from the alternator's BAT terminal.

Now try connecting the battery cable again. If there's now no arc, the short is in the alternator - time to replace it.

However if you still get an arc, there's have a short somewhere in the charging system wiring. Disconnect components (ammeter, ign switch, etc.) one at a time until you find it.

JdubyaM · Mar 23, 2014

Thanks Bob. I will give your suggestion a try tomorrow morning. If I do have to go further and check the ign. switch and the ammeter, I will need to unscrew the instrument panel and pull it back and I will need to make sure the battery is disconnected when I do that. This is a very nice tractor and I want to make sure there are no issues. If I can't find the problem I plan on sending it to a local tractor repair shop and have him troubleshoot and repair or replace all the wiring. I am not sure the previous owner changed the ammeter when going to 12v. I read where you are supposed to use a different ammeter when converted to 12v.
JW in Georgia

Steve@Advance · Mar 23, 2014

The 6 volt system that was original to the tractor would have been a positive ground, as in the + (positive) terminal of the battery would have been connected to the chassis or engine block. That must be reversed to use an alternator. If it wasn't reversed, the alternator is probably damaged.

Be sure the battery is connected with the - (negative) terminal to chassis before further testing or replacing the alternator.

Here is an example of the alternator wiring changes that must be made.

http://www.expeditionlandrover.info/Delco_Alternators.html

Also the ignition coil needs a resistor added or replaced with an internal resistor 12v coil. Wire the + side to the ignition switch, the - side to the points.

Any lights will also need to be refitted with 12v lamps.

buickanddeere · Mar 24, 2014

(quoted from post at 22:32:36 03/23/14) I am not sure the previous owner changed the ammeter when going to 12v. I read where you are supposed to use a different ammeter when converted to 12v.
JW in Georgia

The ammeter is not voltage sensitive and does not require replacement. It will how ever need the leads swapped terminal to terminal so it doesn't read backwards . Now that the previous owner" fixed" a problem that did not exist with alternator . Which up the voltage to 12 from 6 and the chassis polarity to negative to positive.

James Howell · Mar 24, 2014

Take a look at this link on YT for information on a <a href="http://www.yesterdaystractors.com/articles/artint195.htm">Step by Step 12-Volt Conversion</a>.

Have used this wiring diagram to rewire our 54 Model 40T and 54 Model 40S.

Take a look at the photos below of the Model 40S wiring that was completed last Saturday.

Hope this helps.

JdubyaM · Mar 24, 2014

Thanks James. This will be a lot of help for me trace down the short and/or replace the wiring. Wonderful!
JW in Georgia

(quoted from post at 14:59:10 03/24/14) Take a look at this link on YT for information on a <a href="http://www.yesterdaystractors.com/articles/artint195.htm">Step by Step 12-Volt Conversion</a>.

Have used this wiring diagram to rewire our 54 Model 40T and 54 Model 40S.

Take a look at the photos below of the Model 40S wiring that was completed last Saturday.

<img src="http://photos.yesterdaystractors.com/gallery/uptest/a151025.jpg" width="650" />

<img src="http://photos.yesterdaystractors.com/gallery/uptest/a151026.jpg" width="650" />

<img src="http://photos.yesterdaystractors.com/gallery/uptest/a151027.jpg" width="650" />

Hope this helps.

JdubyaM · Mar 24, 2014

Thanks Steve! This will help me a lot! I sure do appreciate it.
JW in Georgia

JdubyaM · Mar 24, 2014

These photos are great James! Thank you VERY much!
James W in Georgia

Bret4207 · Mar 25, 2014

Could someone explain this "exciter switch" idea? What is it and what are you using for it? I understand the alt needs to have a current draw to "kick it into gear" and start charging, but what does the switch do?

ETxJohn · Mar 25, 2014

Bret4207

the exciter switch is anything ( momentary switch, light bulb, diode etc. that will throw voltage to the no. 1 terminal on a 10 SI gm alternator. The momentary switch can be connected to battery voltage, the light bulb or diode needs to be connected thru the ignition switch.

Bret4207 · Mar 26, 2014

Gotcha, thanks.

John Deere 40 Has Short Draining Battery After 12V Conver...

Member

Well-known Member

Well-known Member

Member

Member

Well-known Member

Member

Well-known Member

Member

Member

Member

Well-known Member

Member

Well-known Member

Member

Well-known Member

Well-known Member

Well-known Member

Member

Member

Member

Well-known Member

Member

Well-known Member

Similar threads