Hello, a couple month ago I changed the air conditioner condenser, now that winter just start my furnace heater is not working, it is showing intermittent blinks,and said the polarity reversed,I checked the transformer is working giving 24 volt out,but , it do not have power comint to furnace draft inducer ,and the ignitor,the fan is working fine,I think the Board is bad, but ,I not sure, is there any way to know is my board is bad?