I've had a Passport 7500 for about 7 years and it's worked flawlessly. However, now when I turn it on there's no response (no audio, no lights). The vehicle power plug works for other 12volt plugins, the 2Amp fuse in the power cord was fine but I replaced it anyway but the unit still doesn't get any power. Prior to this, there weren't any issues with it shorting or working intermittently. I believe the last time it worked was last week in Missouri where it was 90 degrees and I forgot the unit on the windshield for several hours with the windows closed. Could I have cooked it?