I have a Rheem pool heater model 2 66a the display is not working but the heater turns on and heats the pool. Nothing works on the display?

SOURCE: Rheem water heater, will start but flame lasts 10 seconds

Is the vent fan working well and can you feel unobstructed air out the termination fitting outside?

SOURCE: raypak pool heater piliot light on heat will not turn on

Make sure that gas control knob is set to ON (counterclockwise). Make sure that ON/OFF switch is ON. Check that temperature setting is high enough to call for heat. Make sure pool pump is running and water is flowing to unit.
If not above there is a diagnostic procedure on page 33 of manual at:
http://www.raypak.com/uploads/6000.52AG.pdf

SOURCE: When Heater is turned on display shows 125, doesn't ignite/fire.

I am not sure if you have solved this issue, or not, but here is one idea. When you turn on the heater, it is reading the temp at 125/126 correct? IF this is what the heater is reading, then the problem is the Thermistor,or temp sensor, and is very easy to replace.

If you have an Owner's Manual, there are part numbers and instructions on how to replace the Thermistor. If you do not have one, follow the link below and it will take you to one online:

http://www.pentairpool.com/pdfs/MaxEThermOM.pdf

SOURCE: Rheem water heater turns off by its self

Flashing code 76 is lost communication between the remote and the burner control assembly CCA (circuit card assembly). The CCA is still under warranty if purchased within the last 3 yrs. Contact Rheem customer service and have your Mod. and S/N available....explain to the agent you are recieving - flashing code 76...they'll walk you through the process.

SOURCE: Solution for Jandy Lite 2 Pool Heater display flashes on & Off ..

Can a model LJ250P Propane 2005 model be installed indoors . The rating plate says it can. But manual says it cannot. What the hell????