Textbook Problem

To answer the following questions refer to Figure 12–10.

When the thermostat contacts close the blower motor starts and the heating elements turn on normally. When the thermostat contacts open, the heating elements turn off and the blower motor stops running immediately. Which of the following could cause the problem?

1. a. The thermostat contacts did not open.
2. b. The flow switch contacts did not open.
3. c. The fan thermostat contacts did not close.
4. d. BMR coil is open.

FIG. 12–10 Air flow must be present before heating elements can be energized.