Battery drain, clicking noise

[opus104132]

I posted this question yesterday but it never showed up. Trying again:

I've searched extensively and can't find anything on this. My 2003 S is draining the battery quickly when off with key out and locked or unlocked (<12V in a day or two). I hooked up my Amp meter and found that the rapid drain stops when I remove fuse C3. I think the cause of the drain may be related to a clicking sound coming from directly in front of the trunk. The noise happens exactly once every 60 seconds and stops when I remove the C3 fuse. Can anyone identify the noise? Below is a video of it. The sound is at about 15 seconds.

https://youtu.be/rwl3OCCaBoE

I've replaced the battery and verified that charging system is OK. If someone can identify the sound that will at least point me in the right direction.

Thanks for any ideas!