I have a two-bulb F28T5 light fixture that went out and replacing the bulbs with new ones did not fix it. So I replaced the ballast with a new one. The lights come on but go out within a second or so. I cleaned the prongs that hold the light with alcohol and a Q-Tip but that didn't help.
I bent the prongs inward slightly and then the bulbs stayed lit for at least five minutes, long enough that no one noticed when they went back out. I tried rotating the bulbs in their sockets again but, as before, they only stay on for a second and go out.
The only thing I can think is that, perhaps, one of the bulb holders is bad or loose but, with it staying on as long as it did before, I wonder if there's something I'm not thinking of.
Best Answer
If the lights actually light then apparently the lamps and wiring are good. I would suspect the ballast.
Is your ballast rated for T5 or T8 lamps?
The 'F' on the lamp is just the wattage rating.
I believe the two lamps are incompatible with the ballasts designed for them respectively. A lot of the T5 ballasts are listed as high output or HO. shop for ballasts and I think you will find they are lists for one or the other but not both.
You need the lamps that match your ballast.
Good luck!