My attic fan stopped working, I swapped it out for a new fan with thermostat. Still not working, I suspect that recently installed LED lighting in my kitchen may be causing this problem with the attic fan. After I moved into the house 17 years ago, the attic fan stopped working. The put in a new fan then, but the fan continued to not work. I finally tracked the problem down to CFL bulbs that had been put into by outdoor house lights. Once I replaced the CFLs with normal incandescents, the fan started working again. The only thing I've changed lately is installing those LEDs in the kitchen. I had assumed that the attic fan was on the same circuit as the outdoor lights, so the kitchen upgrade wouldn't effect it, but now I'm not sure. I'm about to call an electrician, but I'm wondering if there is something else easy that I can check to fix this problem. I'm also open to the possibility that the LEDs are NOT the issue. Thanks
Your fan is wired in series with the lights
When the person installed the fan, the wires that he needed (hot and neutral) simply were not available in the box he wanted to tap. So he did something crazy like tap across a light switch (hot and switched-hot).
Anyway, there's a reason he did it that way: doing it the right way was too difficult. So you should expect the solution to this to be non-trivial and may involve fishing some cables through walls.