Rheem Raypak Heater Troubleshooting


New member
Jun 13, 2020
I have a Rheem 336a atmospheric pool heater that is about 11 years old and am looking for advice on troubleshooting. I realize the heater may be reaching the end of its life but has been working reliably until recently.

Symptom: Heater sparks, fires up and water temperature starts to rise as expected. After 20-30 minutes, flame shuts down. It will attempt to spark again with no success and then continuously display "CFH" with no error codes. Once powered off and allowed to sit for 5-10 minutes, it usually relights upon power on. Will then run for a few minutes and flame shuts down again. In all cases, temp set point is not reached.

I have checked the transformer and temp sensor and they are working fine. Flame sensor does not appear to be unusually dirty. Sand filter is backwashed and pressure is normal. Water flow from main drain and strainer are OK. Just a guess but it seems to happen once the unit gets hot as the heater starts reliably from a cold start. Again, no error codes to point me in the right direction.

Any suggestions on what else might be the cause?

Thank you in advance.
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