[daveplot]

I have two 4 bulb T12 Fluorescent fixtures in my basement. During the winter they turn on fine, but over the summer due to high humidity they won't turn on. I know it's the humidity since they're fine after I run my dehumidifier for a while.

Would a new T12 ballast fix the problem, or is this inherant with T12 fixtures? I have a lot of T12 bulbs, so i'd prefer not to upgrade the entire fixture to T8. Would I be able to replace the ballast with a T8 one and operate the T12 bulbs ok?

 

[joed]

Never heard of humidity causing the problem you describe. Perhaps the ground connection needs to be fixed.
Yes you can replace a T8 ballast into a T12 fixture. Just make sure follow the wiring diagram on the ballast. It will be different than the T12.

 

[junkcollector]

Would a new T12 ballast fix the problem, or is this inherant with T12 fixtures?

It might, and it might not. My money is on the ballast though. Check all the connections first. My order with flourescent lights is change the bulbs, if that doesn't fix it, I replace the ballast. Sometimes the sockets go bad (the bulb's pins fail to make contact) I usually convert to T8 at that time. They seem to be less affected by humidity, and can take colder temperatures.

I have a lot of T12 bulbs, so i'd prefer not to upgrade the entire fixture to T8. Would I be able to replace the ballast with a T8 one and operate the T12 bulbs ok?

The bulbs must match the ballast. So no you cannot put T12s in a light with a T8 ballast.

Otherwise I agree with Joed