Just wanted to reply to this ancient thread and offer a solution since I had the same issue and got it resolved. Manuals were no help and neither was the Hayward tech line.
Situation: Hayward Goldline Aqua Logic controller, model PL-P-4. Front panel which is normally displaying something all the time was going off and on, and occasionally beeping like it was resetting itself. Couldn't control the pump or lights unless you happened to hit the proper button during the brief period where the display was on.
I just replaced the display and it worked. Part number for my model was GLX-PL-LOC-P-4. Expensive little bugger. $389 from eztestpools.com was the cheapest option I found, but still cheaper than replacing the main board.