Which four steps should be taken during a no-heat call?

The four steps outlined in the answer choice are crucial in diagnosing and troubleshooting a no-heat situation effectively. Beginning with the thermostat is essential because it serves as the control system for the heating equipment. If the thermostat is malfunctioning or set incorrectly, it can prevent the system from firing up or operating correctly.

Next, checking the fuel supply is vital; in an oil heating system, ensuring that there is actual fuel in the tank is a basic yet critical first step. Without fuel, the burner cannot operate, leading to a no-heat condition.

Verifying power is also a necessary action in this sequence. It's important to ensure that the heating system has an active electrical supply because a blown fuse, tripped circuit breaker, or disconnected power line can render the system inoperable.

Lastly, interviewing the customer allows the technician to gather valuable information regarding the heating system’s recent performance or any unusual behavior noticed before the no-heat condition. This can provide essential clues that might assist in diagnosing the issue more effectively.

These four steps are logically sequential and focus on the fundamental elements that affect a heating system's operation, which underscores their importance in resolving no-heat calls effectively.