I've successfully lit the heater after blowing out the bottom and cleaning the contacts. The ignition sparked for about 8 seconds and it finally kicked on. It stayed lit for about 30 minutes, no smoke or anything unusual. When I turned the pool off for a split second to switch from service to auto mode, the heater will no longer light. I switched back to service mode just to check and still nothing. I do not see the ignition sparking. What could the problem be?