Greetings - I am trying to get my Laars LT400P-L pool heater going again. It used to work, but has not been used in 3-4 years (house rented out). The pool has been in use the whole time. When I turn on the heater (on spa or pool setting) nothing happens for about 2-1/2 minutes and then I get error lights "Service" and "air flow". The service diagnostic guide mentions the tubing - not an issue as fan won't come on. For fan not operating - it says correct the fault. I isolated the fan and put power on it and it works fine. What should I check next to see why the control circuit will not power up the fan?