Dealer installed, yer screwed. I bet they didnt even use the right
color wires. Your just gonna have to get out the old VOM.
I gotta do something similar this weekend. My bilge pump doesnt work,
doesnt even read 12V at the pump, weird, gotta be a break somewhere
where the wire runs through stuff. Gonna have to somehow snake in new
wires.
Could it have been a voltage transient from a nearby lightning strike,
somebody start up a big pump etc? You'd think it woulda fried the
electronics 1st though.

good luck