rando

OK, so there are a couple of issues with Ricky's mod.

First, his circuit (initially) powers the opus from the car's ign/acc line. That may be fine on some cars, but in general, is a bad idea. You don't want to try to draw (upto) 15A from your ignition line. Since it's just used to bootstrap the Opus, it probably only draws a few amps max. Just the same, that's a heavy load as far as the ACC line is concerned. That's why most of us have run a custom circuit to supply the 12v line on the opus.

Second (and probably worse), once the Opus turns on, the 12v line and ign lines in your car will be shorted. The 12v line is probalby a high current line with large guage wire. The ignition circuit (being a low current circuit) is almost certainly using 18-24guage wire. Ignition circuits are usually protected by 15A or less (7A in my truck) fuses. If an ACC line shorts anywhere in your car, it is liable to release magic black smoke since the ACC fuse will no longer protect it. THIS IS BAD. VERY VERY BAD.

There is an easy solution. Use two relays. The switch side of the relays are in parallel and switch the 12v line. Hook up one of the coils through a 12v output of the opus. Hook up the other coil to the ACC line. Throw in a couple of diodes to block EMF if you like.

Instead of the second relay, you could also try throwing in a couple of diodes to assure that the ACC and 12v lines stay isolated. This would have the annoying side effect of lowering your 12v line input voltage and thus the opus' low batter protection circuit would then kick-in sooner.

Good luck.

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2004 4runner