When furnace starts up the combustion Air blower runs than after a few seconds the furnce ignites but then when the circulation fan is susposed to turn on, it doesn't. I did test the ACB Heat terminal on the circuit board for 115VAC but comes back with no volts. And flame then goes out and get a LED code of 4 flashes. So then I checked the resistence on both of the circulating fan switchs. The result that I got was that both switchs were closed. would could possibly be the problem?