ENGINE STALLS

Hi! I got a problem with my 2003 mitsubishi montero sport. When I make a stop or turn the engine stall. But when I am using a/c the rpm stays @ 1, so it doesn't shut oFf the engine, but sometimes didn't work. The problem started when I forgot to turned off the light, so I charged the battery. Thought something's had a problem with the battery and even changed it but never resolved the problem. I have changed the fuel filter. Indicators like brake and check engine soon lights (amber in color) are on. If anyone could help me. Thank you.