OK guys, need a second brain to sort this out. I decided to wire the camera to the OPUS, use a relay, and put an override switch. Phew!
OK so this is strange. I first wired the camera directly to OPUS, with a fuseholder on the + line. I put a 1 Amp fuse, and it blew. Ok, so this means the camera draws more than 12 Watts?! Yikes! So I put a 2 AMP fuse, and it did not blow. tested for a while, all was fine, so I proceeded with the more complex wiring using relay and switch etc.
So here's what's strange... after wiring it all, it is blowing a 2 Amp fuse. So, it is drawing more than 24 watts (2amps x 12V = 24 Watts).
Note that I tested the coil voltage on the relay (control circuit) and it was a nice 12V from thr acc as expected, and also tested the high voltage circuit of the relay before connecting the camera, and it had a nice 12V too coming from the OPUS. But as soon as I connect the camera, it blows the 2 Amp fuse!
I have not tried a 3 Amp fuse yet, but this is getting ridiculous. more than 24 Watts for the camera?! Ouch.
Any ideas what's going on?