The condenser fan on my 14 yr old heil 4-ton gas pak is running while the heat is on. I know its not supposed to but I'm not to sure where to start trouble shooting. My first instinct is the control board or the digital thermostat, (7 yrs old ) Can some one point me down the right path?

Exact model number of unit.

A good guess on my part is that the contactor/relay for the condenser fan motor is stuck on and need to be replaced.