Furnace Blowing Cold Air in Richmond

Furnace Blowing Cold Air in Richmond

Richmond runs on heating. Summers sit in the 60s to low 70s off the bay, and a lot of homes here have no AC at all, so the furnace is the one piece of equipment that actually gets leaned on. When it starts blowing cold air, it gets noticed fast because the house has nothing else to fall back on. The good news is that 'runs but blows cold' is almost never a dead system. It is one component in the ignition or control chain doing its job badly.

The most common version we see in Richmond is a furnace that fires for a few seconds, the burners drop out, and the blower keeps pushing room-temperature air. That pattern points at the flame sensor or the hot surface igniter, both cheap relative to the whole machine. The second most common is simpler than people expect: the thermostat fan is set to ON instead of AUTO, so the blower runs around the clock and pushes unheated air between heat cycles. We check the dumb stuff before we sell you a part.

In the older post-war stock through central and south Richmond, the furnaces are old enough that we also test the heat exchanger and CO levels on the same visit. A cold-air complaint on a 20-plus-year unit is a good moment to confirm the thing is safe as well as heating.

Common causes

Flame sensor coated with carbon. The sensor proves a flame is present. When it gets a carbon film, the board reads 'no flame' and shuts the gas off seconds after lighting, so the blower runs cold. We pull and clean the sensor, recheck the microamp signal, and replace it only if it will not hold. This is the single most common cold-air call we run in Richmond.

Cracked hot surface igniter. On modern furnaces the igniter is a thin element that fails open over time. No glow, no light, blower still cycles cold. We ohm it out and look for the crack. Replacement runs roughly $200 to $350 depending on the unit, and it goes on the written estimate before we touch it.

Thermostat fan set to ON. Fan ON means the blower never stops, so between heating cycles you feel cool air at the registers and assume the furnace failed. We confirm the setting, explain the difference, and move on. No charge for a setting, and we would rather find this than sell you a repair you do not need.

Gas supply or valve issue. A furnace that tries to light but never sustains can be starved for gas, a partly closed valve, or a weak gas valve solenoid. We confirm supply pressure and valve operation before condemning anything electrical. On older Richmond homes a tripped or sticky valve is more common than a failed board.

Limit switch short-cycling on an old unit. A dirty filter or blocked blower lets the furnace overheat, the high-limit trips, and the burners shut off while the blower keeps running to cool the heat exchanger. You feel cold air. We check filter, blower wheel, and airflow, then test the limit. Often it is airflow, not the switch.

How we diagnose it

• Confirm the thermostat fan setting and the call for heat at the board before assuming hardware.
• Watch a full ignition cycle: igniter glow, burner light, flame sense, and whether the burners hold.
• Clean and test the flame sensor, and ohm-check the igniter for an open element.
• Verify gas supply and gas valve operation on furnaces that light but drop out.
• On units past 18 years, test CO and inspect the heat exchanger while the panel is open.

$75 diagnostic, credited toward any repair over $200. You get a written quote before any work begins.

Furnace Blowing Cold Air in Richmond: common questions

Nearby and related

Furnace Blowing Cold Air near Richmond: Berkeley · Oakland .

This is usually a furnace repair in Richmond job. See our furnace repair overview or the Richmond service area.