The dome light has 12volts hot to it all the time, the door switches and dash dimmer ground the other wire to complete the circuit. It sounds like you have a short to ground and that is keeping the lite on, also draining the battery if the hot is shorted.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy