I have a Carrier Weather Master 9200. I have tried everything I can find on the internet to try and it still doesn't work. I am getting an error code 31. I have tested the heating sensor and it tests fine, I have checked to make sure there are no clogs in the tubes connected to the pressure switch, I tried to bypass the pressure switch but still cannot get heat. The blower initially kicks on and runs for about 90 seconds before shutting off. What else can I possibly try before I have to call a repair person?