Installation BOSS 9990 POWER **** IS ON BUT NO SOUND

Did you hook up the brake wire (it is usually pink) to ground? If not hook wire it with the ground wire on your stereo.

When put in reverse the image is up side down
The links above may or may not help. Good luck.
http://blog.qualitymobilevideo.com/backup-camera-system-installation-guide-trigger-wire/

the 2 power lines to supply batery and black to ground blue to speaker

If you charge without a resistor, there will be a large spark. If you know how to wire, you can charge the cap through a light.

Wire from the (+) battery to one lead of the light, then the other lead of the light to the (+) on the cap. This will charge the cap a little slower. When the light goes out you can hook it right to the battery.

yes the red is your power and make sure you have the ground hook up also and the yellow should be your memory why which it should be hook up to a wire that has power all the time

get a small led or something that runs on 12 volts. i use my 5 dollar 12v test light and hold it to the positive cable thats gonna be hooked to my cap.
hook the other side to the cap, it will light up the test light and in a minute or two the light dims and then goes out, after its out , the cap is charged......JUST DONT LET IT TOUCH THE OPPOSITE WIRE WHEN YOU HOOK IT UP OR YOU DISCHARGE IT and its not funny

make sure the yellow wire has power all the time and the red wire has power when the key is on. Most likely you do not have power to the red.

ITS BEST TO HAVE A SOLID REMOTE WIRE WITHOUT NE SPLICES WAT SO EVER

there is a wire that is called remote. that is the wire that cuts off the radio when the power is killed. you should have a red wire that is power a black wire that is negative and usually a yellow wire that is the remote wire. there is a wire coming out of your stock radio harness that is on when the ignition is on, and off when you cut the key off. that is the wire you want to hook the remote wire too. if the remote wire is not there, you can hook that yellow wire to anything in the car that is on when you turn the key on but off when you turn the key off, its called acc. you probly have yellow and red both connected togather.

Either the radio is bad out of the box (Very possible with the BOSS brand) or you car has factory amplifiers that need to be turned on. This is aaauming ther sound system played prior to the installation of the new radio. Most vehicles you can power up the amplifiers simply by connecting the BLUE remote turn on wire in the harness, but can get tricky in some vehicles.
Post the year make, and model of your car, and I can shoot you some odds/info about factory amplifiers.