Finding a draw

[jmg343]

My stock batteries lasted almost 6 years, most of which was spent living in Northern California. Then I moved back to NY where the climate changes more and is colder. I replaced the stockers with 2 Interstates about 3 years ago I'd say. Now they are either shot, or I have a serious draw somewhere. If I let my truck sit for more than a day or so, it will be dead when I go back out to start it. Completely dead. I confess that I am not the best at electrical work on vehicles. I have wired everything myself as far as gauges, lift pumps, fog lights, etc go. But I have no idea where this draw may be coming from. Is there any way to find out, or rule some things out? I would hate to buy 2 new batteries only to find that the problem still exists. I've searched on here but have not found any concrete answer.

As soon as I can I am going to check the wires from the alternator, starter, etc and make sure that nothing has rubbed through creating a short. Any thing else I should focus on?

thanks
Jake

 

[JoshH]

You can unhook one of the batteries and then hook an amp meter inline with one of the cables on the other battery. That will tell you if you have an excessive power draw. To rule it out, you'll have to start pulling fuses to see if you can make it stop.

 

[jmg343]

Thanks, I will try that. Should I do that to both batteries? Unhook one, amp meter on the other. And then vice versa?

 

[Sledhead]

Yes. It could also be a bad (shorted cell) in one battery drawing them both down. Charge both batteries good then disconnect them from the truck and each other. Measure the voltage after a couple hours and they should be the same, hopefully about 12.45V

 

[JoshH]

Thanks, I will try that. Should I do that to both batteries? Unhook one, amp meter on the other. And then vice versa?

The test I'm describing will only test the amount of amps the truck is drawing on the batteries while the truck is off. The reason you have to disconnect one of the batteries is because the meter won't read anything if the other battery is disconnected. There should be no reason one side would test any differently than the other unless your batteries are somehow isolated from one another.

 

[jc1843]

When you first connect the meter, it will show a large draw, because the computers and clock need charging. If you connect the meter to one battery- and have a good connection, then disconnect the other battery-- that way the computers will stay charged up.

You may have a bad battery-- you can do the Redneck load test. Disconnect one battery, and see how it starts, then connect and disconnect the other battery and see if it starts the same.

You can also just turn on the lights and other accessories [engine off] and check the voltage of each battery. Be sure one is disconnected-- and do the test described above.