something is draining my batteries

Just get a DMM and see what kind of amp draw you have off the batteries with the key off. If its drawing a couple amps, start pulling fuses 1 by 1. If that gets you no where, check and see if the alternator is pulling current.

 

have been charging batterys and disconnecting them then check drain on batterys left front two connected and took hot and ground off third battery front batterys have 12 volts after 26hrs back 2 droped to 9.5 hot cable on third battery was off but I left jumper cable from 3 to 4 on batterys so this would tell me the draw is off 4th battery anyone know what it powers

 

If you have relay switches for your side boxes push them In and test that they close and turn the light off.

My 2015 Western Star had one that stuck on, drove me crazy because I always turned the Main switch off but our garage would do a PM while I was gone from the truck for 2 days ,to come back to dead batteries.

Went round and round with our garage before I happened to catch a crack of light coming from up under the bunk one night.

 

does your truck have a battery kill switch mine don't having the same problem you are charge youre batteries and take off the cables from the forth battery and see if the front three hold 12 volts mine would go dead in 10 hrs have traced the draw to one of the back 2 batteries checking the third battery now the front two have been at 12 volts for 26hrs with the rear disconected

 

Being a boat guy and living with battery banks and house batteries all my life I can not figure out why these trucks don't come with main switches and the ability to isolate at least half the battery bank.

 

no lights on anywhere draw seems to come to battries 3 and 4 I am checkin them know seems to come from 4th battery not sure what it powers

 

All 4 batteries are connected together. They all power the same stuff.

If that one battery is dying, chances are its toast. Get them all load tested. If one battery fails, replace the group.