The response of a switch supplying electrical power to a load is periodically tested to ensure proper operation and control over the switch. In the event the switch does not respond to commands from a controller during a test cycle to turn off and open a circuit supplying power to the load, a short circuit is created by a test switch. In this event, a fuse is automatically blown preventing uncontrolled power from reaching the load. In one example, the load can take the form of a resistive heating element in an electric heating blanket or electric heating pad.