Is there a simple way to check to make sure the blower is the issue. Diagram would help along with written insturctions.Thank you Larry

I have a 1973 F150 and am having trouble with my heater. I am pretty sure that the fan or blower is the main problem and not the heater core itself. At times the blower will start and then stop. At this point I am thinking that either the switch is bad or there is a loose wire somewhere. I would...