Intermittent MH Bulb

[t4stock]

About a month ago, I installed two 175W 15,000K to replace my 10,000K bulbs. The bulbs have worked fine, except that one bulb is noticeably brighter than the other.
Q #1: Whyis this?
More importantly, hte dimmer bulb (perhpas a coincidence) no longer stays lit. When I turn my lighting system on, both bulbs get that blue glow inside while they heat up, but only the one (brighter) bulb lights. The dimmer bulb heats up, lights for about a minute, then goes off. his repeats all day.
Q #2: Doea anyone have ANY idea why this is happening?
Thanks!
Todd

 

[sonny]

Are they both new bulbs? When a MH lamp is getting ready to burn out, it will generally start shutting off intermittantly. I recommend swapping the lamps in the fixture, so you'll know if it is a problem with the lamp or the ballast. If the same lamp acts up, return the lamp if it's new, or replace it if it's older than a year. MH lamps should be replaced about every 12-18 months due to shifting spectrum problems. When you replace lamps, don't replace both at the same time. Give it 2-4 weeks between replacing. If the other lamp does the same thing, you have a bad ballast that will need replacing.
Sonny

 

[t4stock]

Well, I switched the intermittent bulb with an old MH I had for emergencies and sure enough, the old bulb lit right up. Thus, I think it is a problem with the bulb not the ballast.
How should I present this problem to the mail-order co. Do you expect he will give me grief about returning the bulb?