Own a 2002 Chevy TB with about 90k The lighting system is very dim when the vehicle is idling When the gas pedal is applied the lights get bright Whats the problem Can I repair myself?

another test that you can do befor desid to change the battery ,first get a good mulimeter or DC voltmeter , then start the car, switch OFF all electrice devices like interior light , outsid light , radio, offcorse AC ,while the engine is runing disconect the posittive batery conector from it ,then test the voltag between the car chasse and the disconected positive battery pole .. if it reades from 12 to 14 volt this mean the car ulternator is ok . then the battery need to be replaced ,,, dont forget to choose good brand with same AMPS capacity..... good luck