Is it blowing anytime or is it not blowing at all? Just asking this question because a lot of my customers say their heater/a/c is not working when the blower is not blowing. The heater was working, when checking the system I'd realize there was no air blowing so they could not feel the heat.
Make sure the heater core is getting hot by checking the heater hoses at the core at firewall. Both hoses should be hot to the touch at normal operating temp. If not but one, probably stopped heater core, if neither, possible low coolant level or thermostat. If both are hot, possible bled/temp door actuator.