Mysterious Dead Battery

[hemiboy]

OK forums members, here is one that I hope someone has experienced before.

I have a 2004 G35 6MT that likes to drain the battery every 4 days or so. Everything will be fine for 4 days (multiple starts per day and miles driven) and after the 4th day the battery will be dead. I'll jump it, drive it around to charge it (14.5V @ battery) and all will be fine for another 4 days or so.

The car is electrically stock with the exception of a Sirius radio that was installed before I bought the car (I assume it is a dealer installed unit). The battery is holding a charge (checked it with my load tester) and the alternator is charging (output load test). A few months ago I noticed a problem where either the radio didn't "acknowledge" the Siruis unit, or the Siruis unit was not "talking" to the radio. This disappeared after the next dead battery.

So with this information I am guessing either the radio is pissy and isn't turning off the amplifiers when shutdown, or the Siruis isn't turning itself off when the car is shutdown. These are only guesses right now. This week I am going to gin up a shunt resistor and start measuring current through different fuses to see if there is a device not turning off.

Has anyone noticed this behavior before? Has anyone had one of these radios or Sirius units fail? Any other thoughts?

Thanks in advance.

[poormansporsche]

Hello and welcome to 6MT. I haven't seen the problem you're describing, but I wanted to offer an idea for troubleshooting it. Perhaps given that I'm generally lazy, I usually look to gather the most/easiest info on a problem before I start tearing into stuff and testing circuits,etc.... so, if you have a bit of time to work with, you might just pull the fuse for the radio overnight (parked at work too?) and go for 4-5 nights to see if it happens again. It's pretty simple to do and the troubleshooting value is huge. A variation would be to pull a few fuses for systems/circuits that might be the most suspect; benefit being possibly a faster result...negative being you'd have to go ahead and narrow it further from there. Best of luck in your troubleshooting.

$.02