So you put a 12v muffin fan under your deck for added cooling? Good idea! It gets pretty hot inside that stereo console.
What you might want to do though, is tap into the wire that is connected to your switched source from the ignition. That way, when the wire is hot....the fan comes on (in accy or ign on mode only).
Or, you could do it this way: connect a 12v relay to the switchable wire coming off the deck (amp turn on wire) and provide the relay with a constant 12v source. When the deck comes on, the wire from the deck shows 12v, closes the relay and turns your fan on. When you power the deck off, fan shuts off (no need for a switch unless you really want one instead).
I may try this myself, if I can find a quiet enough fan.
What you might want to do though, is tap into the wire that is connected to your switched source from the ignition. That way, when the wire is hot....the fan comes on (in accy or ign on mode only).
Or, you could do it this way: connect a 12v relay to the switchable wire coming off the deck (amp turn on wire) and provide the relay with a constant 12v source. When the deck comes on, the wire from the deck shows 12v, closes the relay and turns your fan on. When you power the deck off, fan shuts off (no need for a switch unless you really want one instead).
I may try this myself, if I can find a quiet enough fan.