Raypak RP2100 starting problems

I have a Raypak RP2100 (ng) heater for my inground pool. It is 15 years old and haven't had any notable problems yet with it. I have replaced the "message board" for lack of a better term about 3 years ago. The only way to see temp and such is on the Jandy inside the house. I went to start up this year and all I got was a clicking sound coming from behind the " message board" panel. I removed the panel and noticed the black "orion" relay was clicking. It doesn't do anything else. I'm under the assumption that the circuit board may have taken a %&$#. There was a ton of rust under the unit on the floor when I opened the cover. It's been getting progressively worse over the last five years or so. Is this unit worth fixing? How much is a circuit board? How can I find out IF the board is toast, or if that's the problem? I don't smell gas, and the igniter doesn't work. Sorry for the long winded post, but I felt the most info would insure the best answer. Thanks in advance.

Hi, Bill, and welcome to the Pool Forum!
I'm so sorry that I can't help with this problem but hopefully someone will be able to!

. . . I'm not sure if anyone active on the forum is experienced with that particular heater.

I'd recommend Google-ing for "Raypak RP2100 starting problems" and seeing if you come up with anything. There are several pool forums that have a much higher percentage of pool service guys among their members, and they may have discussed problems like yours.