I have a five year old Raypak 207A on my 500 gal spa. When I turn the unit on, the display shows: PV 1, then CFH, then SPK, then the burner ignites, then CFH again, then it displays the flame icon and temp for 20-30 seconds, then it cuts off. Then the whole cycle repeats. Then it shows FAN. I have cleaned baskets and changed out the filter.

CFH means "Call For Heat", and SPK is "Spark". It sounds like you are running out of gas.Propane tanks need to have 30% in the tank for a heater to run correctly,and after they are filled you must bleed the air out of the line.If you have Natural gas,the gas line may be too small to supply enough gas to keep it running. NOTE...gas pressure MUST be checked with the heater running.