Mike PleziaInside service technician, Clark Associates · Commercial Equipment, HVAC, and Refrigeration professional

The No-Heat Call: A Calm First Path

27 Sept 2026 · 1 min

Watch on YouTube

1:25

In this instructional video, the speaker guides tradespeople through a systematic, safety‑first approach to troubleshooting a no‑heat furnace call. The advice begins with staying calm and confirming that the thermostat is set to heat, the set point is above ambient temperature, and the furnace is actually receiving a call for heat. The speaker then outlines basic checks: verifying power to the furnace, the service switch, breaker, door panel, and inspecting the filter for blockage, which can trigger a limit switch. The core of the tutorial explains the typical gas‑furnace start sequence—inducer fan activation, pressure‑switch vent verification, igniter heating, gas valve opening, flame sensing, and main blower start—emphasizing that noting the exact point where the sequence stops directs subsequent testing. Safety directives include never bypassing safety switches, avoiding repeated breaker resets, turning power off before handling wiring, using appropriate meter settings, and adhering to company procedures due to the hazards of electricity, gas, heat, and moving parts. Finally, after any repair, the speaker advises running a full heat cycle to confirm safe operation. The overall message is to be methodical, prioritize safety, and share the knowledge with others.

Chapters

Hey! Are you new to the trades? Here's something you may not know about approaching a no heat furnace call. Start calm. No heat does not automatically mean a bad furnace. First, confirm the thermostat is set to heat, its set point is above room temperature, and the system is actually receiving a call for heat. Then check the basics: power to the furnace, the service switch, the breaker, the door panel, and the filter. A dirty filter can cause overheating, which can open a limit switch, a safety that stops the burners when temperatures get too high. Next, follow the sequence. Watch what the furnace does after the call begins. Many gas furnaces start the inducer, a small fan that clears combustion gases. Then they prove venting through a pressure switch, heat the igniter, open the gas valve, sense flame, and start the main blower. If it stops, note exactly where it stops. That point directs your test. Do not bypass a safety switch or keep resetting a breaker. Turn power off before touching wiring, use the right meter settings, and follow your company procedures. They are there because furnaces involve electricity, gas, hot surfaces, and moving parts. After the repair, run a full heat cycle and verify safe operation. Stay safe and systematic. Now that you know, you can help someone else know.