Disconnect cables at fuel pump and glow element of glow-spark plug.
Turn heater on. After about 130-200 seconds (at nominal temperature and 68 F/30 C ambient temperature), the safety switch should break the circuit to the relay (contact A).
If the safety switch has operated within the required time, press lever on safety switch in direction of arrow and turn heater on again.
Honeywell safety switch only:
If a correction has to be made, move adjusting screw through slot in lever as follows:
Response time too long: Turn screw clockwise.
Response time too short: Turn screw counterclockwise.