Purex 400 Triton MiniMax Plus - I think the controller is bad because...

The heater will ignite with flame to all burners and after about 20 seconds or so flames will go out. Wait a few seconds (maybe 10?) and flames will ignite. Cycle continues. I let it do this for awhile thinking there may be air in the system and it had to purge itself. Didn't help.

The controller is a HP S8600F or S8600F1000 (1) and has another # on the side that reads 9947 V. I checked the electrical connections to the controller and all appeared OK (no crusty ends for lack of a better term).

I've never messed with something like this. It's my father-in-laws new purchase and I'm the lucky one to help out as he's on a budget and needs the heater as part of his therapy. The home was built in 1999 but I don't know the age of the heater. This is an in-ground "spool" and is in Arizona so there is no rust evident on the heater, external or internal.

Could it be anything else? If you think it's the controller, were would I find the best pricing and what part numbers supersede this part number if it is no longer available?

I had a similar issue last year but the cycle lasted about 5-10 minutes each. It turned out to be a bad hi limit pressure switch. Goodluck and let me know how it works out