metal halide light question

at work today i took down a 400w metal halide light used for temporary power. i work construction. it was not working properly. the light has been used before on other jobs. the bulb lights up a little like it is warming up but never gets to its full brightness. they said they were gonna throw it away so i took it home. i didnt try another bulb in it. do the bulbs do that when they are at the end of their life. my boss thought it was a ballast problem but he didnt know. if the ballast was bad would it still light the light up at all. can someone please help me so i can fix it and get it in my grow room

Ballast problem.... The ballast also do this when you turn them off and and then back on right away. Check the ballast, dotn worry about the bulb.