I just cleaned the tub, and filled it getting ready for the Summer. This is a Coleman Horizon Series. I would guess it's about 8 or 10 years old. It was built into a deck on the home we bought a few years ago. It was running fine last fall when I shut it down and emptied it for our Michigan winter. Now the filter pump pulses off and on for about 15 seconds, and then shuts off for about 15 seconds. Then starts cycling again. Pump 2 runs fine. Blower runs fine. Heater is not coming on. It's a problem to work on since there's only about 30 inches of head room under the deck.