M1009, rear battery dies

[1 Patriot-of-many]

Bought new batteries last winter. The rear battery(closest to firewall) keeps going dead in a week or two. Glow plug system functions properly when battery is recharged. Dash meter shows okay in the green after starting the truck. Front battery stays charged. What should I look for? Or do i just have a bad battery?

 

[jcollings]

Did you confirm each battery With multimeter separately getting Around 14 V When running after starting?

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[WWRD99]

I'd charge up that rear battery with a slow 10 amp charge for several days then get it load tested. After that being it is the 12 volt feed is look for a draw. The somewhat common one is the alternator...can test for that very easy.

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[1 Patriot-of-many]

Did you confirm each battery With multimeter separately getting Around 14 V When running after starting?

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No, Where do i attach the leads right at the battery terminals? Thanks

 

[1 Patriot-of-many]

I'd charge up that rear battery with a slow 10 amp charge for several days then get it load tested. After that being it is the 12 volt feed is look for a draw. The somewhat common one is the alternator...can test for that very easy.

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Okay I will do that, I have a load tester. How do i test the alt for a draw? Thanks

 

[WWRD99]

Okay I will do that, I have a load tester. How do i test the alt for a draw? Thanks

I'd use the 12 volt block up by the glow plug relay...stick the dvom in there and see what volt draw you have. Unplug the alternator.

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[1 Patriot-of-many]

I'd use the 12 volt block up by the glow plug relay...stick the dvom in there and see what volt draw you have. Unplug the alternator.

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dvom?

 

[WWRD99]

dvom?

Digital volt meter

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[1 Patriot-of-many]

Thanks I kinda thought so, but wanted to make sure

 

[jcollings]

No, Where do i attach the leads right at the battery terminals? Thanks

Each battery separate just to confirm both alternators are working properly.
As mentioned, after charging that rear battery, let's sit and then carbon pile test to confirm it's a good battery.
Check your fuse block for melted terminals also problematic on these trucks.

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