Green light in bottom left on when device plugged in the mains, but cannot be switched off and no display

Un plug it from the mains.

since how long are you facing the problem

Remove Mains Plug and press Standby switch from LED Panel for 30 sec.
Press Input & Ch Down Switch from LED panel and plug in and start LED
LED will start and "K" will appear on screen
Press Ch Down & Vol Down switch at same time
You will get 1/10 page on screen
Go to 9/10 page by pressing left & right button from remote
Select EEP and press Ok button from remote
After 30Sec remove main plug and restart LED.

These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices. http://electronicshelponline.blogspot.com/
Blinking codes details of many popular brand TVs are given. Surf the site with patience. If blinks continue without any pause, the main board [One see at the left side; Green coloured] is faulty.

How many times switching the light? Count it and text me to tell you

• Turn the Navman off by holding the power button in the upper left corner of the device until the screen goes blank.
  
• Plug the unit into its charger using the USB port on the bottom of the unit. The battery indicator light next to the power switch should turn orange, indicating that the device is charging. Once the light has turned green the charge is complete. If the light does not turn on, verify that the car charger is plugged into a working outlet.
  

Those blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices.
http://electro-medical.blogspot.com/
http://homenol.blogspot.com/
http://electronicshelponline.blogspot.com/
If blinks continue without any pause, the main board is faulty.
Search the site by type in the "brand name" to your device, in the "Search box at the top right of the display window of the Homepage" to get gathered related posts.

i had same problem today, it had locked up during deal/no deal
unplugged it three times nothing happened, wouldn't switch on
unplugged again left it for 5 minutes
then plugged in and left alone for 15mins plus
lights flasing then evetually green light went
all ok

Yes :
You should replace the PCU if prints show any of the following symptoms.

• Colors are missing, faint, or partially blurred.
• Toner smears appear.
• White or color rivers appear.
• White or colored streaks appear.
• 1. Important: Switch off the device and disconnect it at the mains.
  2. Open the right side cover.
  3. Pull the green levers as shown to release the inner cover.
  4. Lift the inner cover upwards.
  5. Squeeze the green lever on the black PCU.
  6. Pull the unit carefully out of the device and dispose of it in accordance with your local environmental policy.
  7. Place the new PCU on a flat surface.
  8. Peel off the tape from around the new PCU.
  9. Remove the top cover from the PCU. DO NOT remove the bottom cover at this stage.
  10. Rest the new PCU in the device as shown.
  1. Push the PCU into the device while holding the bottom cover. You will hear a click when the PCU has locked into place.
  2. Lower the inner cover.
  3. Push the two green levers as shown to secure the cover.
  4. Close the side cover.
  5. Connect the device at the mains, switch it on and wait for the self-test operation to finish.
  6. Please remember to rate all users who assist you for free :)
     

I’m happy to assist further over the phone at https://www.6ya.com/expert/joe_8b8c2cd6ce148309

Here is a wiring diagram of the radio by wire color:

Radio Constant 12V+ Wire: Green/Yellow
Radio Switched 12V+ Wire: Yellow/Black
Radio Ground Wire: Black/Green
Radio Illumination Wire: Light Blue/Red
Radio Dimmer Wire: n/a
Radio Antenna Trigger Wire: Blue
Radio Amp Trigger Wire: Blue (Same as Antenna Trigger)
Front Speakers Size and Location: 5′ x 7′ Doors
Left Front Speaker Wire (+): Orange/Light Green
Left Front Speaker Wire (-): Light Blue/White
Right Front Speaker Wire (+): White/Light Green
Right Front Speaker Wire (-): Dark Green/Orange
Rear Speakers SIze and Location: 5′ x 7′ Rear Deck
Left Rear Speaker Wire (+): Gray/Light Blue
Left Rear Speaker Wire (-): Tan/Yellow
Right Rear Speaker Wire (+): Orange/Red
Right Rear Speaker Wire (-): Brown/Pink
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