pool heater quits

I have a TELEDYNE LAARS Lite pool heater.
Just did spring start up - the pilot light works well.
the heater starts - stays on for 2 to 5 minutes - then shuts off . I flick the on/off switch to off then on & the heater starts up again ( the water is only low 50s) & the cycle repeats....
help! thanks ....

this is generic, not specific to your heater...

I'd look closely at the flue to make sure it isn't obstructed - maybe a mouse nest or something like that. It sounds like it is a safety circuit that is shutting it down unless the thermostat is bad. Is the pump circulating the water properly? If not, the water in that small volume of the heater could easily get hot enough to inform the heater it has reached temp. Could be clogged or the flow restricted - maybe some leaves?

heater

You have to test every safety device to see which one is doing it, THEN figure out why. It could be a pressure switch, or a flow switch, or a high temperature switch due to poor circulation,