I have a Hayward HD150FD heater on my spa. I set the temp and mode 5 years ago, and haven't touched the keypad since then.
The other day, when I fired it up, I had an AO error code. Before I knew what that meant, I tired pressing all the buttons, but there was no response.
I took care of the AO error (some critter had chewed through the vacuum hose). I was hoping that with that fixed, the keypad would work, but it doesn't.
The heater still heats up to 104, where I originally set it, but the mode button does nothing. The up/down buttons don't do anything either, but maybe that is because I can't put it in Standby mode.
Interestingly, when it fires up, the Standby light remains lit orange, even though it is running, and the Heat and Spa lights are on.