I have a Teledyne Laars Lite pool heater Model LLD 250N. When I turn the heater on it will run for 10 minutes and turn off. If I turn the power switch off and right back on it will run agin for 10 minutes and shut off.

turn gas valve to pilot hold down for 1 minute keep holdibg and light pilot hold for 2 minutes then turn to on

make sure the orfice directly below the flame rod is lighting could be a spider web blocking that burner

temp sesor goes into top right of the heat exchange follow the copper syphon loop it is right next to it

make sure it is a propane heater propane burns hotter than gas if not correct heater it will overheat if ok check gas pressure if not enough heater will overheat you also might have too small gas line and are emptying it

safety switch is opening and closing, or issue with gas valve coils

Have you checked the power tot he ignition control? If you post the model number of the ignition control I can provide you with specific troubleshooting charts for your specific unit.

You have no flame rectification.....LLD series heaters check for a signal through the flame to ground; if the module does not detect this signal, it go through two more trials for ignition and then lock out the module. There should be a flame rod and it may need cleaning. I use steel wool.