Raypak 2100 335A digital heater not working, please help

This heater starting acting up by constantly cylcling on and off. Also, the LCD display still worked, somewhat, but the charators looked like they were flikering on and off to the point where it was difficult to read. The switch membrane looked corroded and when I pressed and applied pressure to it, the heater seemed to stay on, but shut off as I let go. So I replaced the membrane switch with a new on and the heater seemed to work fine for a little while, but the LCD display still looked to be malfuncting a little. But as long as it worked, I really didn't care. Now the heater won't turn on at all. When I power the unit up, the LCD display shows what appears to be PP 22 for a few seconds and then the off comes on, and the water temperature does not come on. Once I hit mode to turn the unit on, PRS comes on and stays on. I checked the pressure switch and it seems to be functioning properly, I can feel it click when I turn the pump on and click again when I turn the pump off. I even jumpered directly across the presure switch terminals, basically bypassing the switch all together with no change in the heater, LCD still shows PRS.

Any ideas? I think I need to repalce the PC board/control board, but really don't want to spend $300 just guessing.

Thanks

Anybody able to help Stan?

This is a year old so I'm sure you have it fixed, but I have the same heater. It's the circuit board. I've replaced two. Make sure when you replace you get the new LCD read out with it or you won't see the LCD numbers as you describe. My second one is on the way out and I'm here trying to decide whether to get a new heater or replace the board AGAIN.