For he past couple years my dad has had problems with his pool heater. Sometimes we could bang on it and then it would start up. I have heard of pressure switch problems... But maybe it could be a bad thermostat? When we jumper the TH & PG (I think those were the two), it would make it fire up and most of the times after that it would stay running. Sometimes it just runs good, then all of a sudden shuts off even though thermostat was set at max and pool for sure wasn't as hot as it should be for a max setting. Any ides or tests that can be done to pinpoint the problem part?