Why does my stock stereo display flicker from dim to bright when I have my headlights on? How do I fix it?

2002 F150XL w/ no CD or cassett

 

There must be a loose connection on the wire from the radio to the headlamp circuit. It has a wire that sends a signal to the radio to dim the display when the lights are on. This signal must be coming and going. Try taking the radio out and putting it back in. This may fix a loose connection on a plug somewhere.

 

Need to take stereo out anyhow so I will take a look at the connection. Do you know of the correct pin # on the plug that I should be looking for or should I just use the meter and test for the 'lights on' active wire.

Thanks for replying.

 

look for light blue with red stripe wire.

 

cool