323 ma. Is way too much. That's a third of an amp. A typical glove box lamp draws about half an amp. Unless specified differently by the manufacturer, 35 ma. Is the maximum allowed to keep all the computer memories alive. Chrysler says at that rate, a good, fully-charged battery will be strong enough to start an engine after sitting for three weeks. Cadillac is the only manufacturer I'm aware of that allows more. That is 50 ma.
The first thing to consider is if someone installed an aftermarket radio and wired it incorrectly. If the radio doesn't turn off with the ignition switch, or if it keeps a remote amp turned on, the battery will be dead overnight.
The next thing is most vehicles now have one or more computers that need up to 20 minutes to go to "sleep" mode. Until they do that, they can draw up to three amps. That makes measuring current drain a challenge because it will blow the meter's internal 2 amp fuse or you have to switch to the 10 amp scale. That can mean moving the positive meter lead to a different jack. That, and simply switching to lower scales for more accuracy creates a momentary open circuit, and that is enough to wake up those computers. Then you have to start all over with the waiting for them to go to sleep mode.
The solution for this is to use a jumper wire to short out, (bypass) the amp meter while you switch meter ranges. Once you're on the range you want, you can remove the jumper so the current has to go through the meter.
On a truck as new as yours, the computers are going to be turned on by a digital signal from one master computer when the ignition switch is turned on. It is not likely one computer will fail to turn off, although an internal driver circuit could be shorted keeping its circuit turned on. Most of the time that will be detected by the affected computer when it's in operation and it sees something is not responding properly. It's much more common to find a light bulb staying on or something like that. One other thing that can do this is the generator's voltage regulator. Most of them now get a turn-on signal when the ignition switch is turned on, but they also have a circuit that is tied directly to 12 volts all the time. You can identify if that is the cause of the drain by unplugging it while monitoring the current drain. Next would be to start unplugging fuses to see which circuit is affected. I don't like recommending that anymore because so many manufactures have designed in tricks that cause computers to lock up requiring a trip to the dealer.
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Monday, March 2nd, 2015 AT 3:11 PM
