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Discussion Starter · #1 ·
I recently acquired a late 70s Ford 3600 diesel and have been having some issues with the battery staying charged. I purchased a new battery a couple months ago and it started without any problems for a few times. When it wouldn’t start I checked the voltage on the battery and it was reading around 8V. I charged the battery and the same thing happened again. I had the alternator tested at a repair shop and it checked out ok. I then replaced the voltage regulator. Forgot to mention that I checked voltage before starting and after the tractor is running and also with increasing the rpms and the voltage stays the same around 12.4 (doesn’t appear to be getting charge from the alternator...but it tested good according to shop). What should I check next? Any help is appreciated!
 

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Do you have an ignition/indicator light on the dash, this has to glow when the ignition is switched on and when the engine is started, the light should go out, does this happen for you, if the light doesn't glow when the ignition is switched on, then there will be no field excitement to get the alternator to charge, that is if your tractor has this light.
 

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Hello Junkman, welcome to the forum.

You may have a short somewhere in your electrical system that is draining your battery. Common problem with these old Ford diesels. 12.4 V is not enough voltage from your alternator, but it might be pulled down by a discharged battery?? Should be 13.5 - 14V. I would charge the battery up and then check the voltage. If the voltage remains at 12.4, your alternator is not putting out.

Disconnect your battery next time you finish with the tractor, and see how it cranks next time you want to use it.

If you have a short in your electrical system, it is imperative that you find it and fix it. Disconnect the battery whenever you are not using the tractor. Below is a picture of my Ford 3600 about 30 years ago, because of a short circuit.
 

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Yes, disconnect the battery when leaving it for a while. I installed a battery disconnect switch on my tractor, and installed a solar trickle charger to the grill to keep the battery topped up in the winter. Has worked well for me.
 

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This model came with different alternator solutions. Could you post a picture of the backside of the alternator, clearly showing how the wires are connected to it?
 

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Discussion Starter · #6 ·
Hello Junkman, welcome to the forum.

You may have a short somewhere in your electrical system that is draining your battery. Common problem with these old Ford diesels. 12.4 V is not enough voltage from your alternator, but it might be pulled down by a discharged battery?? Should be 13.5 - 14V. I would charge the battery up and then check the voltage. If the voltage remains at 12.4, your alternator is not putting out.

Disconnect your battery next time you finish with the tractor, and see how it cranks next time you want to use it.

If you have a short in your electrical system, it is imperative that you find it and fix it. Disconnect the battery whenever you are not using the tractor. Below is a picture of my Ford 3600 about 30 years ago, because of a short circuit.
Thanks for the reply, I actually fully charged the battery yesterday and checked voltage before starting and after and it was around 12.4-12.5 both times (no change while the tractor was running). Do you happen to have a wiring diagram for a 3600?
 

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Thanks for the reply, I actually fully charged the battery yesterday and checked voltage before starting and after and it was around 12.4-12.5 both times (no change while the tractor was running). Do you happen to have a wiring diagram for a 3600?
Yes, but a picture would tell what system you have. If we do not know that, you can not get the proper diagrams.
 

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By the way, the picture I posted is from a Ford manual, and shows a ground terminal connection that is a bit weird. Either they got it wrong, or there was another type at the time. I doubt the latter.

Anyhow, your ground connection is right, according to the alternators that are out there. You can check if one of the studs on the negative diode bridge (the two studs to the right) has an insulating plastic washer. That one is not for ground, it is a connection for a tachometer. The non-insulated stud is for the ground connection.
 

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Discussion Starter · #14 ·
By the way, the picture I posted is from a Ford manual, and shows a ground terminal connection that is a bit weird. Either they got it wrong, or there was another type at the time. I doubt the latter.

Anyhow, your ground connection is right, according to the alternators that are out there. You can check if one of the studs on the negative diode bridge (the two studs to the right) has an insulating plastic washer. That one is not for ground, it is a connection for a tachometer. The non-insulated stud is for the ground connection.
Thanks, just had quick question. If I were to switch out the wires on the output and the regulator on the alternator is it going to cause any harm if they were correct already?
 

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If they are correct already you do not need to switch them.
Trace the wires back to see what they connect to. The wire that goes to the starter solenoid battery post, or some other point in contact with the battery (+) cable, shall be connected to the output terminal (#3, figure 2). The other wire is spliced, one leg to the regulator, and one leg to the light on the dash, and is connected to the regulator terminal (#4, figure 2).
 
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