I have a Breckwell SP22. Recently, it began running the room blower fan on HIGH, immediately at start-up, and no matter what heat level is set. I took everything apart and cleaned both fans inside and out. I have been reading about testing the high limit sensor and low limit sensor, the blower motor itself, or that it could be a bad control board. I am new to electricity stuff. I have a multi-meter - I am just wondering for sure where to start and how to do it correctly. Any help would be greatly appreciated! Thanks!