BATTERY DRAIN

[zeik]

Hi guys. This new to me in the last month 939a1 was working and starting fine for few weeks. Came out couple days ago batteries dead and would not take a charge or boost. Threw two new batteries in and it died overnight. Diagnostics so far is nothing is wrong with the switch. Not to say that's been eliminated just that it appears to be working. There is definitly a heavy draw on something. Also to note I haven't done any kind of changes or maintenance since I got the truck. It's in the shop now and we are trying to diagnose why 2 brand new batteries could die overnight. Thanks for your help in advance.

 

[ericp351]

Hi. The classic drain-check is not complicated, but some times takes a while. Break the circuit- like pull the main 24V hot. Then put your amp meter in series, that wire/ cable to the bat post where it was. All amps draining will now read. Be careful to use a proper fused meter- correctly set. Then "play detective". Disconnect (Isolate sounds fancy) your "loads" (stuff), wire by wire until the meter reads 0 or a few mill. amps. Good luck! Sometimes "man-handling" a dirty switch will show the trouble. Don't exceed the meter setting or at best you will need a fuse.

 

[juanprado]

Possibly sticking solenoids in pcb box?

 

[msgjd]

other than the items already mentioned, i have occasionally run into parasitic drain caused by the alternator

 

[M35A2-AZ]

Above is all good things to check. I have put a battery cutoff switch on all my trucks.