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Ted G.
Ted G., ASE Certified Technician
Category: Chevy
Satisfied Customers: 6138
Experience:  20 years auto repair experience, ASE Master Tech, Mechanical Failure consultant, Expert Witness
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I have a 2007 Chevrolet 2500hd duramax and the batteries will

Resolved Question:

I have a 2007 Chevrolet 2500hd duramax and the batteries will not stay charge. If I charge them up and drive it it will last but if you let it set in the yard for about a day the batteries are dead. I have installed three sets of batteries and it still does it can you help me.
Submitted: 7 years ago.
Category: Chevy
Expert:  Ted G. replied 7 years ago.
You have a parasitic draw on the electrical system. This means there is too much current being drawn even when the truck is turned off. It is a fairly easy test to check it. An ammeter is installed between the battery and the cable and draw is measured. if it is more than 100mA (50 is better) then you start pulling fuses until the drain drops below spec, whatever is on that fuse is the failed part. Usually it is a module or electronic device not powering down when turned off.
Customer: replied 7 years ago.
The truck is dead now do I need to charge it and get to crank and then do this. I am not much of a mechanic but I can follow your lead. The truck should be off after it is charged.
Expert:  Ted G. replied 7 years ago.
It just needs enough battery voltage to run the accessories so an hour or so of charge will do it. Turn everything off, disconnect one terminal (usually positive) from the battery and put an ammeter in between the cable end and the battery so all current is pulled through the ammeter. Make sure the doors are all closed too. Occasionally it can be something stupid like a glove box light.
Customer: replied 7 years ago.
Called the mechanic and he said he all ready did that and the ma was good.
Expert:  Ted G. replied 7 years ago.
If you are killing batteries overnight there has to be a drain. It is possible it is intermittent and didn't show up originally. Occasionally we have seen modules re-awaken after sitting for a while. (Land Rovers do it when a plane flies too close, better not live near an airport LOL) What you may need to do is set it up for the test and leave it be over a day, checking regularly throughout the day. If suddenly the meter jumps up, you are ready to start diagnosing.
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