Jeff @ Velocity Motors.

Sorry for the late reply, the Mazda radio is basically a Ford radio so all the connections are the same as in a Ford. The two wires that are in question looks to me like a dimmer and an Illumination wire. To test this out, take one of the two target wires and attach to a DMM or light tester. Now probe the target wire and turn your lights on. If the DMM did nothing before and is registering 12 volts that's good, now turn your dimmer up and down. If the light tester dims with the turn of the dimmer switch, then the target wire is your dimmer wire. If the DMM number fluctuates with the dimmer switch then this is your dimmer wire.

If the lighter or DMM does not fluctuate but does register when you turn your lights on, then this is your illumination wire. Normally this connection is not necessary on most newer decks because they all have their own illumination circuit now.

Hey !!!! Just wait one minute there !! I was getting to your post but I have been trying to get to it systematically seeing that I'm doing an install inbetween answering posts and trying to gather information.

Anyway, if you probed the target wires with 12 volts and the display turned off, chances are you may have blown a resistor that was needed for the illumination. There would not have been traces of burned electronics smell because it would only have been one resistor. It may not have affected the actual display rather the back light would have been damaged. This is why the display would shut off from a 12 volt surge in the wire. If it is infact your dimmer wire, it does not receive a full 12 volts rather a regulated power supply through a pot.

Give me your email address or email me at techsupport@velocitymotorsport.com and I will email you all the available diagrams for the Mazda vehicles that I have. There is detailed information on eachof these diagrams as to what wire is what and the polarity as well. Just hope that it is current enough to cover the 2000 + radio's.