Set t-stat fan to auto, turn on the heat. Follow the wires from the fan motor to the control board. There is one tab labeled as heat and one as cool. With your multi meter set to volts, set one lead on heat and the other lead to neutral. Within 90 seconds, of the flame being established, you should get 120v. If you don't it is likely something is amiss with the board. Likely, hard to say for sure without being on site.