Furnace turns off heat and fan continues blowing cold air.
Carrier split unit Model 58RAV055-GC Circuit Board at Furnace CES0110057-00
Natural Gas
I am experiencing a problem with my heat. I have a programmable zones thermostat and noticed that the air was not coming out hot when it was suppouse to be. The temperature was set to 75 but the temperature in the room was only 68. The thermostat shows that the heat it is suppouse to be on, but the heat it is not at the furnace.
I checked the control board for the zone system and the LED's for the heat are on showing power for the furnace. I checked the voltage here and it is 24V. I checked the voltage at the W and R C at the furnace and it is 24V. Then I checked the voltage at the gas valve and it is not getting power.
Normally, the heat does work for 10-20 minutes before turning off the heat, but the fan does not stop.
I am starting to conclude that the circuit board it is the problem, but I am not sure about some logic:
Is the flame sensor suppouse to sense all the time that there is a flame so the fan should start?. if so, then should not the flame sensor open the circuit for the fan to stop when there is not flame anymore?. or is this logic just at the start, and then other type of sequence takes place?
I want to make sure I checked every scenario before I decide to make the expense of the board.
Any help would be greatly appreciated.
Thanks