No heat blowing

There are several possible reasons why your blower, vent, defrost, AC, and heater might stop blowing air:

1. Blower Motor Failure: The blower motor is responsible for blowing the air through the vents. If the blower motor fails, you will not get any airflow from the vents.
2. Blower Motor Resistor Failure: The blower motor resistor controls the speed of the blower motor. If the resistor fails, the blower motor may stop working or only work at one speed.
3. Fuse or Relay Failure: A blown fuse or faulty relay in the blower motor circuit can prevent the blower motor from working.
4. Control Module Failure: The HVAC (heating, ventilation, and air conditioning) control module is responsible for controlling the blower motor and other components. If the control module fails, it can prevent the blower motor from working.
5. Vacuum Leak: If your vehicle uses a vacuum system to control the vents, a vacuum leak can prevent the system from working properly.
6. Broken Blend Door: The blend door controls the direction of the airflow. If the blend door breaks or gets stuck, the air may not flow through the correct vents.
7. Wiring or Connector Issues: Faulty wiring or connectors in the blower motor circuit can prevent the blower motor from working.

check for a good ground for the blower motor as if you have 12 volts at the motor it indicates a problem motor or no ground wire to complete the circuit

It would help to know the make and model. Different manufacturers put them in different places and mount them different.

Check for a bad fuse.

check blower motor and resistor with test light,