Hello, I've inherited a pool with many problems, I am going to attempt to fix them myself because the pool people I've been dealing with are idiots. First problem I want to address is the sta rite heater, model sr400 na. The heater fires up, then shuts down within a minute or two. The control panel reads that it needs service. I don't have a manual so I don't know what can be serviced. I did see via google that there is a thermostat that can be checked. Any other sugestions?