I have an Intertherm Nat. gas furnace,. Model # MMHA - 056 - AAHR -05. The small vertical Booster motor (Cumbustion Blower Motor ) runs constantly. The Thermostat can be set at 80 deg... and the actual room temp. will get no more than 62 deg. The blower ( fan ) motor works fine coming on, and shutting off as required but the furnace is just not putting out the heat that it is capable of. Any suggestions as to what the problem could be would be greatly appreciated.

Regards

Wayne