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Discussion Starter #1
2006 2WD Single Cab, Long Bed.

I am having problems with the electrical system drawing down batteries overnight. Shut the truck down and use fob to lock doors and turn on security system. Also, I make sure no interior or exterior lights are on when I leave. At the truck in the morning, both batteries were completely discharged, as in 0.1 Volts. Not good.
I was told on another blog to change out batteries. I did that. Two fresh batteries. This did not work, as both batteries discharged again. In fact, they were discharged so bad, they did not test good after a two day slow recharge on trickle charger. So I took out batteries and returned them for exchange. Again, two new batteries. Again, overnight same scenario, both batteries discharged. So at least I know the problem is not the batteries. I recharged these slowly and they have no load voltages of 12.65 and 12.8 volts. So I assume they are good.
Also, I have disconnect both batteries and checked the current flow between the neg post and the neg lead. The current measurement was about 3 milliamps. That is below the range that I've read for most trucks when static nothing turned on or running. This is probably from onboard computers and probably radio memories.
That is the history. So now I must find the culprit that is drawing down the batteries. How do I accomplish this? I do have a nice digital multimeter and can follow specific directions regarding circuits. I also know where the fuse boxes are located. Any help?
 

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Are you sure you were using the meter correctly? 3mA doesn't sound correct even for a normal truck. If you are killing 2 batteries overnight you should be getting a couple amp draw at least. Many meters you have to move a lead to a different socket than normal to do an amp test. You can also try that test with a light bulb like a tail light. If there is a draw the light will light. Brighter the light the larger the draw. Worst case the light bulb burns out which is a lot cheaper to replace than many meters.

Once you do find a way to read the draw then you start removing fuses till it goes away at which point you at least know the circuit involved.
 

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Here are some videos that will help you understand what to do:


And if you need more infomation of a different look, go to Youtube and search for 'parasitic draw'
 
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Discussion Starter #4
Are you sure you were using the meter correctly? 3mA doesn't sound correct even for a normal truck. If you are killing 2 batteries overnight you should be getting a couple amp draw at least. Many meters you have to move a lead to a different socket than normal to do an amp test. You can also try that test with a light bulb like a tail light. If there is a draw the light will light. Brighter the light the larger the draw. Worst case the light bulb burns out which is a lot cheaper to replace than many meters.

Once you do find a way to read the draw then you start removing fuses till it goes away at which point you at least know the circuit involved.
Thanks 57.
I forgot to say that the parasitic current draw is intermittent. Most of the time the electrical system is drawing about 2mA when pass side battery is only checked (driver side disconnected) and 3mA when driver side connected (pass side disconnected). These I believe are nominal draws when the system is operating normally. I had one attempt where the system was drawing about 400mA from one battery. It was about a week ago with everything turned off. I was unable to find the circuit by pulling fuses to isolate before the culprit shut itself off. So it is an intermittent draw.
 

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More information. I used an amp clamp that was more precise and easier to read. The electrical load was cycling intermittently, however it was pullling about 7amps during each cycle. When not pulling current, the reading was about 50-70mA. The cycling was random, sometimes each 5 or 6 seconds followed by 5 or 6 seconds down to 50-70mA. The next time it would be for 10 seconds, then off for 8 seconds then 2 seconds on, followed by 6 seconds, etc. Each time it was right at 6.5-7.2 Amps. Also when it was very quiet, I could hear the electrical component clicking off. So with intent ears I isolated the problem to the driver side door. Upon further investigation and analysis, I found that when the driver side door was open the cycling stopped. When the driver side door was closed the cycling started again.
So my question is what would cause this cycling of the electrical component in the driver side door? Also why does it only cycle when the door is closed vs open?
 

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Every time you open or close your door, a message is sent to the BCM about that event. That wakes up the computer. You want your truck to be completely asleep when doing parasitic draws. And don't pull fuses, test across the fuse to see if there is any voltage. Cuircuits that have a current flow will also have voltage, and that's what you are looking for by testing across a fuse, one side to the other. And that does not wake up anything. Give you truck at least 30 minutes to go to sleep, then start checking.
 
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