Heater blower motor

Hi guys.
I'm having an issue with the blower motor in my son's 77 volare working intermittently. When it works its great but it will stop working without reason. I changed the switch yesterday and it seemed to solve the issue until this afternoon. The fan makes no unusual noise. Hard to resolve when its random. Irs a pretty simple system.
Any thoughts?
Jeff
Author: /6Volare