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Battery Drain 2011 RAM 1500 Laramie 5.7L Hemi 144K miles


Topic starter

For the last three years I have been having a battery drain issue in the cooler months of the year, even though I keep my truck in a heated garage at 45 to 50 deg F.  Thinking it was a battery problem, I have replaced the battery four times now.  But I am now convinced it is a problem with the truck.

I have done some investigations to narrow down the cause of the drain.

I put an analog ammeter in series with the battery and video recorded the meter and discovered that there is a random battery drain that lasts 40+/- 5 seconds.  The drain will start up again in anywhere from 8 seconds to several hours.  The rapid repeat can last 3 hours.  In one 36 hour period I calculated a 7 Amp Hour drain.  During that 40 seconds of drain it starts at 3 amps, after a few seconds drops to 2.5 amps for about 5 seconds and then settles at 2.0 amps for the rest of the 40 seconds.  There are no sounds or lights happening during these current drains.  The windshield wipers don't budge.

Given the random nature of the current draw, it was impossible to check each fuse by standing there and watching the meter while pulling fuses.  So I built some sensors that would indicate if a draw occurred.  I put one sensor in series with the battery to tell me that a draw had occurred with an LED that would stay lit.  The other two sensors I put into fuse slots.  If the battery sensor and the fuse sensor both lit up, I knew I found the fuse causing the problem. I checked all of the fuses this way. Actually, I found two fuses; M12 and M13.  M12 is the Radio/Amplifier and M13 is the Main #2 Instrument Cluster/Wireless Control Module/ITM/Siren/Multifunction Switch(Steering Column Module).  I just completed modifying the sensors so I can see if the current draw on both circuits is simultaneous or sequential, but have not performed that experiment yet.

Since both the radio (including a satellite radio, no subscription) and the wireless control module are involved, I suspect that the Wireless Control Module is polling the satellite transceiver and not getting the expected response, so continues to request a response. I could easily be wrong.

So my questions are:  1.  Have you seen this problem before and do you know the cause.  2.  Fuse M13 has a lot of stuff on it.  Is there an easy way to disconnect the various components on that fuse circuit, especially the Wireless Control Module, in order to test them individually?

2 Answers

you would need to splice into the wires, or somehow tap into the connectors on the back of the stereo/modules.

Thank you but I don't want to tap into the radio, I want to be able to disable/disconnect the power to the radio and disconnect the power to the Wireless Control Module without disconnecting everything else on the M13 fuse. From your response it doesn't sound like an easy thing to do without dismantling a bunch of stuff. Thanks again.

Why don’t you just unplug your WCM and setup your draw contraption you came up with and see if you still see the draw. If you do not then your WCM is defective and waking up randomly.

If there is no draw move on to the radio and unplug that and re check. It seems you’ve narrowed it down to those to components.  

He said that both circuits were using power. I suspect that pulling the fuse for the head unit will prevent both from waking up. If it does, then I would put a relay on that circuit, and energize it with ignition power.

Topic starter

Well, just to put a cap on this thread, now that the weather has turned warm, I have not had a parasitic draw on the battery for more than a week.  And based on my experience from the last three years, I won't have another problem until next November.  So, until then.  best regards.