Hello,

I'm new here, I joined up because I'm stumped.

I have a 2005 3500 quad cab. I've got a strange battery drain going on. I've charged up my battery using a ctek smart charger so it's completely full. I hook the battery up and the battery can sit for a long time with no battery drain, I've checked the current draw and it stays at 0.02 amps (20 milliamps) which is great.

Now here is where the problem comes in. If I turn the key to accessory and then back off the current draw goes up to 1.5amps for a bit then after about 15 seconds levels off at 0.5 amps (500 milliamps) and stays there. I've isolated it down to fuse 21 (audio-amplifier), when I pull that fuse the draw goes back to the acceptable 0.02 amps, I put it back in and it stays at 0.02 amps. If I also just take the battery cable off for a second it has the same effect.

So I thought my radio must be messed up internally (previous owner had installed an after market radio). I removed the radio and did the same test, it did not solve the draw problem, it once again settled around 0.5amps. Once again I pulled the 21 fuse and that brought it down to 0.02 amps and if I insert the fuse back it stays at 0.02amps.... Sooo, what else could it be? Are there any other items running off that fuse?

I've been pouring over the body builder guide electrical section for fuse 21 (http://www.dodge.com/bodybuilder/2005sbbgl/docs/wd/dr/wiringdiagrams/8w47audiosystem.pdf) and can't figure out what would be hooked up.

Thanks for reading!

Edit:
Just a thought, is the amplifier-radio contained within the radio? Or is it a seperate component?

 

Sounds completely normal to be honest. It takes a good 10 minutes for the truck to really go into hibernate mode. .5 amp draw is normal within that 10 minutes.

 

It was still drawing .5 amps after sitting from yesterday (about 18 hours it was sitting). I leave the hood unlatched so I can open it without going into the cab to activate anything else, the hood lamp is also removed so no power is drawn.

The battery is usually dead and cannot start the truck after 2 days sitting like that.

This is not normal to me.

 

have you done a battery test yet?

 

Not really, but the ctek charger says the battery is good. I've also tried it with two of my old batteries and two brand new batteries. So that's 4 different batteries.

If I break the circuit like I said with a charged battery and hook it backup and do not turn the key to accessory the truck can sit their for weeks and start up just fine. I also have a brand new alternator in there and have measured the voltage when it is running... It's somewhere around 14.4 volts, so it's getting a charge I would assume.

The batteries appear to function normally in that regard. They have enough amps to start easily and the voltages measure correct until they start getting that drain into the system, then they go kaput in a couple days.

 

Are you familiar with a relay? When you wire an amp it has a 12v hot wire and a common ground, what turns the amp on is a signal from the head unit that hits a capacetor, this capacetor acts like a switch for the relay. If it is staying charged after the vehicle has been shut off it means there is a backfeed of power somewhere in the amp. My suggestion is pull the amp and try another amp and see if you get the same draw off the battery.

If you pull the amp and it still happens with the new amp, get out a multimeter and test that signal wire for voltage when the vehicle is off and it is unplugged from the amp, if you have power sitting there, you'll need to remove the deck and check the wiring.

 

Yep! I know what a relay is (although, is it in the radio or outside for my truck?). I don't have a new radio/deck, I just removed the old one and the problem still persists.

I measured the voltage across pins 1 (B+) / 12 (B+) and 11 / 22 (Ground) They measure ~12 volts always key in/out/accessory position, system reset by taking out and putting back in fuse 21. Although I would think since pins 1&12 are straight to the Battery Positive (B+) that there would always be 12 volts no-matter what? I would assume that is to save preset radio stations and whatnot.

I measured across pins 2 (Fused ignition switch (Run-Acc)) and 11 /22 (Ground). No voltage came up at all with the key out or the key in the accessory position. I did not start the truck and try, I assume that is when 12v would hit there.

I've attached the pinout diagram so you can see what I'm talking about:

 

this set up uses the power from the stereo as only a signal. when you turn the radio on its like flipping a toggle switch, the acual relay is inside the external amplifier, if somehow they had a problem when installing the stereo the most logical place to check
would be constant power wich looks to be A114 18GY/RD, this wire is there to keep settings in the stereo head unit, wich is the .2 amps you'll find drawing from the battery. It's entirely possible they tapped into this line if it was an amatuer setup, but not likely if you didn't have this problem before. A diode will let power travel in (1) direction, your amp is littered with them, if this diode goes bad the main power from your big red amp wire might be back feeding and keeping the relay from going back to normal open, this is more likely what is happening.

 

Ok, so funny solution to this problem.

Fuse 21 is for the audio amplifier, which after much reading I find out is only available with the premium audio system on this truck which I do not own. I only have the standard audio system. So I don't have an this amp at all.

The other funny thing that tipped me off is that it was a 15amp fuse in there but the fusebox calls for a 20 amp fuse. I think the guy before me probably installed a new stereo and thought a fuse was needed in there so he threw one in.

Anyways, I just removed the fuse and my stereo still works perfectly. Must be something going haywire in there though when the circuit is active but isn't hooked up to an amp?? Anyways, I'm not sure. I just know now it drops down to the proper amp draw after turning off the key and everything is still working.

Thanks for the ideas.

 

thats more info than i new, i didnt think trucks from dodge had premium audio. Good work.