They are easy enough to test out of the truck. The top yellow wire is 12 volt positive and the black wire is negative. I use a rechargeable battery from Ryobi to test my radios. The other wires in back of radio are for speakers so just grab a old speaker to test. Test the radio outside of truck and see if it still works. Most of the time it is a bad ground in actual truck or even a bad 12+ wire hooked up to it. The other problem can be the volume dial (Potentiometer) can be dusty and need to be sprayed with a cleaner but not WD-40 or the like. I like this stuff
