12V Constant Draw is Draining My Will to Drive

[Fightfan]

I have a 12v constant draw on my 01 2500 HD. I have used a test light on all of the fuses. Nothing seems to be drawing off my battery. I removed the radio fuse from the fuse box under te hood and the batteries still drained over night. Sometimes it takes as little as four to five hours to kill the batteries. It has a brand new starter and the batteries tested good. Is there anything common or something that I am completely missing? Winter is coming here in Ohio and a dead truck=$20k paper weight. Would taking it to the dealer help? Can they test for this crap?
Thanks

[More Power]

If you've gone through the fuses and electrical centers, and didn't find the source of the excessive draw, you could remove the red positive cable connecting to the alternator to see if the alternator is the cause. Be careful with that cable's loose end.... ;)

There is a small & constant electrical current draw, which keeps the security system, radio and ECM/TCM memory powered. This usually takes a few months to drain the batteries.

Jim

[JohnC]

Have you tested the batteries?

[BozDMAX]

It takes a large draw to kill both batteries overnight, probably more than can be read on a standard size multi-meter since those are usually limited to 10A. I went out to Tractor Supply and bought an ammeter for about $9 that will register up to 60Amps, hooked some wires to each end and used that to start trouble shooting. If you just look at the problem from the perspective of reading 'volts' you will miss the problem because several circuits have very, very small parasitic draws that will continue to show volts as you pull fuses one at a time. This process is much easier with two people.

1) Disconnect both batteries, ground side first.
2) Reconnect the ground on the battery on the passenger side.
3) Have your helper hold the ammeter wires between the positive post and the disconnected cable on the passenger battery. If you have a large leak it will register on the ammeter.
4) With your helper reading the ammeter, go thru the underhood fuse box right behind the driver side battery and start pulling one fuse at a time and replacing it if it is not the problem.
5) Start with the large square fuses, since they are the more likely culprits. When you find the right one, the ammeter will drop to zero and you have identified the circuit. If the ammeter drops but not all the way, you likely have more than one problem.

If that does not isolate the circuit...
6) remove the black shroud surrounding the underhood fuse box (somewhat easier to remove the driver side battery first).
7) You will now see several red wires coming into the fuse box area and these can be removed one at a time and checked to see if the current stops flowing.

And if that does not isolate the circuit...
8) now that the batteries are disconnected, get the alternator out of the loop as Jim said, by removing the red wire at the back and bottom of it. I believe it is possible for the diodes in the alternator to go bad and leak current to ground.
9) If you have not found it at this point, it is probably time to take it to the dealer

If you HAVE found it by now:
10) check your owner's manual for the equipment effected by the fuse.

One Caveat: If you have added any aftermarket accessories, take them out of the equation first. I have a 400W inverter installed for running my laptop, for example. Anything like that you have put it should be fused separately and could also be causing the problem.

happy hunting - some electrical issues make my wife start looking for the nice white jacket with the long sleeves...

[hapaschold]

my bought new 2006 dmax battery s barely lasted 1 1/2 years.

in my case i m thinking the lenghty time delay in the remote start caused the problem,

i zeroed out the delay, truck still starts just fine, and we ll see how long the batteries last now.

[Mark Rinker]

I have a 12v constant draw on my 01 2500 HD. I have used a test light on all of the fuses. Nothing seems to be drawing off my battery. I removed the radio fuse from the fuse box under te hood and the batteries still drained over night. Sometimes it takes as little as four to five hours to kill the batteries. It has a brand new starter and the batteries tested good. Is there anything common or something that I am completely missing? Winter is coming here in Ohio and a dead truck=$20k paper weight. Would taking it to the dealer help? Can they test for this crap?
Thanks

Who tested the batteries - were they still connected to the truck, or disconnected and isolated for the test? How many months have they been in service?