Okay so lets gets some detailed background first so you're well informed. I've owned the car for just about 3 yrs. I've replaced the dang secondary amp (I guess technically its not the secondary since it controls a plethora of other things and is technically the stock amp- making the one I installed for the subwoofers the actual "secondary" thats just how I refer to it.) This go around would be the 3rd round. Why I didn't pull it up into the trunk, or make some sort of waterproofing over that rear fender vent the first time around is beyond me, but I didnt... And every winter there will be a bad snow storm that goes slush on the road that I cant avoid driving in... And there goes the amp. Crackling sounds from speakers, then frozen volume/no volume all the audio balance controls stuck in the passenger rear position on the screen. One time no climate control buttons at all, another time ac was fine and just couldn't switch the AC control off so "technically" had no heater. But, no biggie- eBay here I came, part ordered, swapped out battery reset and presto- radio and all controls back. But now I'm here- so clearly thats not the case. Club lexus- I am over the top frustrated!! Please help! So- new amp came in today, swapped it out while resetting the battery.... Connect everything, turn car on, controls, all back- yay! But... Still no sound. Walk to the trunk, to check that all the connections were tight... All seemed fine, walk back to driver seat.... Blank nav display!!! Literally nothing but a blank dead screen as if the car were off. Checked all the fuses, all fine. Used tester light confirming power to the amp- all good. Got frustrated and was ready to rip apart dash- and wife made me post here first before tearing apart her car. What am I missing?

Also if this isnt in the right place, or I formatted something wrong- my bad.

 

I would remove the radio, and with the car running wiggle the electrical harness in the back. Some have reported loose connections from .that harness. I would also inspect the pins in the plug, maybe one pulled off or broke off, that could wipe out the whole screen.

Also are you sure when you plugged everything back together that the nav screen went blank, did you try removing and reloading the nav disc to see if thats working.