M1009 Battery Drain with neutral unhooked

[DaveDawson]

So, I am having a problem with the batteries draining on my M1009. I have even disconnected the neutral and the batteries still goes dead. One thing that I have noticed is that since this problem has started the Gen 2 light does not come on when the key is turned on. Could there be an internal issue with Gen 2? I can find no shorts and am puzzled. How do the batteries drain, when the neutral is disconnected???? Any help would be greatly appreciated.
Dave

 

[Red_506]

Test the batteries individually; they may be bad.

 

[mikes47jeep]

Neutral? This isn’t household wiring

But if the ground or negative is disconnected the batteries shouldn’t drain.

How old are the batteries? My guess is they are just getting old and weak.

And as far as your gen 2 light not coming on I’m just guessing a bad bulb.

Mike

 

[doghead]

Since you have 2 batteries and 2 alternator, are you disconnecting 2 "neutrals?


Test each battery with a digital volt meter, with it running and without and report back with the 4 voltages.

Since you gave us no history on this truck, should we guess it is new to you, or it has been generating fine for the last 3 years? How old are your batteries?

 

[MarcusOReallyus]

What Mike said. There are no "neutrals" in vehicle wiring. Just hot and ground, or + and -.

Batteries do have internal leakage. In a good battery, it's very little. As batteries age, it gets worse.

Batteries can also drain appreciably just from being grungy. If there is a film of old outgassed acid on the surface of the battery, it's possible for that to drain a battery. Not quickly, but it does happen. It actually creates an electrical path between the two terminals.


If the battery is clean, and is still is draining while disconnected, it's probably new battery time.

My suggestions:

1. Clean it up.
2. Charge it up.
3. Disconnect it.
4. Measure it.
5. Wait a day, then measure it again.

That will tell you where you stand.

 

[o1951]

Sometimes it looks like a battery is going dead, but it is not being properly charged. Often that is because of poor battery connections.
As previously stated, acid residue can cause conductive paths and discharge batteries.

Disconnect both battery terminals on each battery.
Clean the batteries,and connectors with a baking soda & warm water solution. DO NOT GET ANY BAKING SODA IN CELL VENTS. Rinse and dry.
Check for corrosion at end of connectors under insulation. R & R if found.

Using a battery post brush, clean all posts and battery connectors until they are bright.
Charge batteries to 14.2 volts and let sit unconnected overnight. Check voltage - if below about 12.5, battery is weak. Replace.

I coat everything with a thin cost of dielectric grease to slow down corrosion, and reinstall connectors twisting side to side to get good contact. Tighten connectors - do not overtighten. Coat exposed surfaces with dielectric grease.

Start truck - after a few minutes, check voltage at batteries. With lights, etc off, should be between 13.8 and 14.2 less and you need to investigate that alternator circuit.

 

[MarcusOReallyus]

I coat everything with a thin cost of dielectric grease to slow down corrosion,.

Ditto! Highly recommended!

 

[DaveDawson]

Both batteries are brand new this week! The terminals were brushed and greased. The batteries will charge. I purchased the truck i July. It runs well. It is completely stock. This is my first military vehicle and 24 volt system. It seems that it is the battery that is closest to the firewall that is discharging.

 

[doghead]

It seems that it is the battery that is closest to the firewall that is discharging.

How did you sense this? Telepathy or VOM?


Test each battery with a digital volt meter, with it running and without and report back with the 4 voltages.

 

[DaveDawson]

No telepathy. Not sure why that was needed, but anyway...... I tested the voltage on both batteries, with all wires disconnected. The back battery was at 8 volts and the front was at 12 volt.

 

[doghead]

And for the third time.

Test each battery with a digital volt meter, with it running and without and report back with the 4 voltages.

The running voltage is critical to tell if you have an alternator issue.

 

[DaveDawson]

This was on the brand new batteries after they had run down. Recharged the batteries and left them disconnected for 24 hours. The voltage was 12 qnd 12, both batteries. Connected. Started the truck. Ran fine. Left the lines connected. Tried to start it 24 hours later and the nothing. Charged again. Started fine. Drove it for a half an hour. Meter was in the green (GEN) the whole time. Disconnected the negative cable. Dead 24 hours later. Have not had time to test the voltages. Will do that tomorrow and report back

 

[DaveDawson]

Will test as suggested tomorrow and report back. Thanks.

 

[Keith_J]

Both batteries are brand new this week! The terminals were brushed and greased. The batteries will charge. I purchased the truck i July. It runs well. It is completely stock. This is my first military vehicle and 24 volt system. It seems that it is the battery that is closest to the firewall that is discharging.

It appears there is a bad diode in the right alternator. Yes, it can charge with certain diode failures.

 

[DaveDawson]

Tested the batteries before charging. the one closest to the firewall was 1 volt. The one closest to the front was 12 volts. Recharged the firewall battery. Both at 12 volts. Reconnected all wires.
Tested the batteries with the truck running. The one closest to the firewall was 13 volts and the front battery was at 15 volts.
Tested the batteries with the truck turned off. The batteries both read 12 volts.
When I first start the truck the meter stays in the yellow until I rev the motor for a few minutes. Then it suddenly pops up into the green and will stays there.

Again, thanks for all of the assistance.

 

[DaveDawson]

Tested the batteries before charging. the one closest to the firewall was 1 volt. The one closest to the front was 12 volts. Recharged the firewall battery. Both at 12 volts. Reconnected all wires.
Tested the batteries with the truck running. The one closest to the firewall was 13 volts and the front battery was at 15 volts.
Tested the batteries with the truck turned off. The batteries both read 12 volts.
When I first start the truck the meter stays in the yellow until I rev the motor for a few minutes. Then it suddenly pops up into the green and will stays there.

Again, thanks for all of the assistance.

 

[doghead]

Rebuild your passenger side alternator.

 

[DaveDawson]

Rebuild your passenger side alternator.

Having not rebuilt one before, can you recommend a place to buy the parts or does it need to be rewound? I will consult the breakdown diagram. I am not afraid of doing the work, but if it needs to be rewound I will have to have that work done.

 

[doghead]

One of our members here, sells a rebuild kit for around $45. CUCV Electric


I doubt your your rotor is bad. It sounds like you have a bad diode(diode trio) or regulator.

I'd rebuild it with his kit. This is something you can do at home with basic tools(you'll need and impact to get the pulley nut off). Or you can take it to a local re-builder.

If you let anyone else work on it, it is imperative to explain that it is a "special" alternator with an ISOLATED GROUND. It has some special plastic isolators inside that must be installed correctly.

 

[DaveDawson]

One of our members here, sells a rebuild kit for around $45. CUCV Electric


I doubt your your rotor is bad. It sounds like you have a bad diode(diode trio) or regulator.

I'd rebuild it with his kit. This is something you can do at home with basic tools(you'll need and impact to get the pulley nut off). Or you can take it to a local re-builder.

If you let anyone else work on it, it is imperative to explain that it is a "special" alternator with an ISOLATED GROUND. It has some special plastic isolators inside that must be installed correctly.

Thank you, sir! I truly appreciate it!