I have a Frigidaire GLMV169 Series microwave (exact model is PLMVZ169 GCC) that is approximately 4 years old.

All of the actual "microwave" oriented functions appear to work when selecting them n the key pad membrane, but the "CLOCK" and the "FAN HI/LO" functions do not work. From what I've researched, and been told by an appliance repairman who provided the part numbers required, the problem would be the Key Pad Membrane Switch (Part #: 5304443989) or Control Board (Part #: 5304468192). From an expense perspective, I do not want to have to by both parts and replace them by trial and error to figure out which part is causing the problem - especialy since the Control Board by itself is approx $130, and the Keypad is $60.

Is there a way to know which part I should replace, or the more probable part that would be causing the problem?