Furnace Repair in Pomona, CA

What is wrong when the furnace will not heat?

Most no-heat calls trace to the ignition train or a safety trip. The control board flashes a code on its LED: a couple of flashes for system lockout, three for a pressure-switch fault, four for an open high-limit, and patterns for the gas valve, igniter, or weak flame sense. We count the flashes, confirm at the part, and fix the actual cause rather than just resetting the lockout.

How does a furnace diagnosis actually go?

We start at the control board, not the burners. The integrated furnace control flashes a status code on its LED, and that code is the map: two flashes for a system lockout after too many ignition retries, three for a vent or pressure-switch fault, four for an open high-limit, seven for a gas-valve circuit, eight for low flame-sense signal, nine for an igniter circuit problem. We count the flashes, then confirm at the part with a meter rather than throwing parts at the board. A flame sensor gets a microamp reading; a hot-surface igniter gets a resistance check; a pressure switch gets tested against inducer draft; the gas valve gets a voltage and inlet-pressure check. Only once the failed component is proven do we quote it. On a genuine no-heat emergency in a cold snap we carry the common parts, igniter, flame sensor, pressure switch, and capacitor, so the fix often happens on the first visit.

Why do Pomona furnaces fail less than the AC?

Climate Zone 9 is cooling-dominant: 60 to 80 days a year clear 90 F, while winters are mild. Furnaces here log few run hours, so they often outlast their paired AC, then fail on a neglected igniter or a flame sensor caked with years of dust. Because the heating load is light, an 80% AFUE furnace is frequently adequate, and a Mitsubishi heat pump can replace both the furnace and the AC in one move.

When should a furnace become a heat pump?

If your furnace needs a heat exchanger, a control board, or a gas valve and it is past 15 years, repair money is better spent on a conversion. A Mitsubishi air-source heat pump heats efficiently through a Pomona winter and carries the heavy summer cooling you actually depend on, often qualifying for utility rebates. In a cooling-dominant Zone 9 market the math leans this way more than it would on the coast: the system you run hardest is the AC, so paying to nurse an aging furnace while a tired condenser limps alongside rarely pencils out. We always quote the straight furnace repair too, so the choice is yours. See heat-pump installation for sizing, or AC installation if cooling is the priority.

How do we check a furnace for a cracked heat exchanger?

This is the safety question behind every no-heat call, because a cracked or corroded heat exchanger can spill combustion gas, including carbon monoxide, into the air you breathe. The tells are a rollout-switch trip, repeated high-limit faults, soot or scorching around the burner box, flames that lift or roll when the blower starts, and an elevated CO reading at the registers. We inspect the exchanger visually with a camera where we can reach it, watch the flame behavior through a heat cycle, and meter CO in the supply air. A confirmed crack gets the furnace red-tagged and shut down, not patched, and that is usually the moment a Mitsubishi heat-pump conversion makes the most sense, since it removes combustion from the house entirely. We carry a CO meter on every furnace call for exactly this reason.

What about the blower and airflow?

An open high-limit (the 4-flash code) is usually an airflow problem, not a heat problem: a clogged filter, a dirty coil, or a tired blower motor choking return air until the furnace overheats and trips. On variable-speed systems a failed ECM blower module can stop airflow entirely while the board still calls for heat. We check static pressure before condemning a part, because a $20 filter sometimes solves a "broken furnace." Leaky ducts make it worse; see duct repair and sealing.

Common questions