chiro

I have a Hayward Astrolite 120v 500w that will stay on for about 15 minutes then turn off for about 30 minutes and then come back on. It will repeat this cycle. The light is only 5 yrs old. Just wondering if anyone has any ideas what could be wrong and if there is any way to fix this without replacing the light. There is no water inside the light and I have already tried to replace the bulb. Thanks.