heater fan is intermittant
Sounds like you need to identify the system, the parts in use, their function, and run tests. The control of the blower could be assumed to just be the blower speed switch? It can be as simple as connector fit. or a ground that's loose. Now you would inspect the connections and function/ wiggle test them. Some blower motors can respond to vibration or being tapped on to start working because they arent maintenanced, but replaced.
Search Chevrolet Blazer Questions
Chevrolet Blazer Experts