Head unit

Did you wire the reverse light yourself? It sounds like your radio is receiving power from the tail lights and not the reverse signal. How did you wire your "trigger" for the radio? Is it tapped on the same wire as your supply for the camera? Some radios have "video sensing" and turn on as soon as it detects a video signal from the camera. It's tough to say without knowing exactly how you have your system wired. If you supply the radio brand and model number, I can look up your manual and see if it has video sensing. I know this answer might not help right away but if you answer a few questions, i'll try to give you a better response. Last question, what wiring harness (car side) are you using / does it supply you with a reverse wire?

Well this is the box that it is plugged in to at the back and also I have no back camera anyway so not sure why it’s doing it . Thanks

Well, It's a wiring issue or the radio. Most radios have a Violet/White "Reverse Gear Input" I would start by making sure that wire isn't hooked up or touching anything. If you supply the make and model of your radio, I can tell you for certain what color the wire is. Let me know that information or once you've checked the wiring. You may also want to check for any firmware updates. Again, if you supply the make and model of your radio I can help you find any of the information about F/W and wiring.

Only a cheep one but this is the one I have . 1. 7 inch 2 Din HD car radio MP5 player with digital capacitive touch screen. 2. Support Bluetooth audio music and hands-free calls. 3. Support Radio function and built-in Aux Input. 4. Support rear view camera input function. 5. 24 hours digital display clock and date. 6. Support TF card(up to 32GB) slot and standard USB interface. 7. Can charge for mobilephone or other USB devices. 8. Support multipe sound effects adjusting. 9. Colorful backlights of power button for decoration in your car.