Why won pool heater light when the pilot is on?
You may have a faulty thermostat that isn’t closing when heat is called for. Also a faulty gas valve could be the problem. Also, be sure that the gas valve isn’t in the “Pilot” position. This is the position you turn the gas valve to when lighting thepilot light. If your pilot light isn’t staying on after being lit, then you may have a bad thermocouple.