Furnace Repair — Furnace Not Heating & Same-Day Service

Furnace Not Heating — Common Causes and What They Cost

• Ignitor failure ($150–$350): The most common furnace not heating call. The ignitor weakens from repeated thermal cycling and eventually cracks or loses continuity. The furnace calls for heat, the draft inducer runs, and the burner does not light. Diagnosed and replaced in one visit.
• Flame sensor dirty or failed ($75–$250): The furnace lights for a few seconds then shuts off. The flame sensor is coated with oxidation from summer inactivity and cannot confirm the burner is lit. Cleaning restores function in most cases. Replacement when cleaning does not resolve it.
• Safety limit switch tripped ($75–$200): The furnace runs briefly and shuts down. Usually caused by a clogged filter reducing airflow until the heat exchanger overheats and trips the safety limit. Check the filter before calling.
• Control board failure ($400–$900): Multiple symptoms appearing at once — erratic ignition, blower not running correctly, error codes — often trace to the control board. Worth replacing on systems under 10 years old. Replacement vs. new system comparison on older systems.
• Draft inducer motor failure ($350–$800): The inducer motor creates the airflow that draws combustion gases through the heat exchanger and out the flue. When it fails, the pressure switch does not close and the burner does not light.
• Cracked heat exchanger ($1,500–$3,500 or system replacement): A safety situation requiring immediate system shutdown. Combustion gases including carbon monoxide can enter the living space. Full furnace replacement is almost always the appropriate response.

When to Replace Instead of Repairing

The 50% rule is the clearest furnace repair vs. replace guide. If the repair cost exceeds 50% of a new furnace installation and the system is 12 or more years old, replacement wins on total cost of ownership in almost every case. Gas furnace replacement runs $2,800 to $6,500 for equipment and labor. High-efficiency models at 96%+ AFUE cost more upfront and reduce SoCalGas bills for the next 15 to 20 years. The contractor calculates the energy savings payback before recommending.

First-of-Season Furnace Failures — Why They Happen

The majority of furnace not heating calls happen in the first two weeks of November. After 6 to 8 months of summer idle, the components most vulnerable to inactivity-related failure are the first to go:

• Ignitors crack from the thermal shock of the first cold-start after months at ambient temperature
• Flame sensors oxidize during summer and fail their first operational test in November
• Filters loaded with dust from spring and summer restrict airflow immediately on first use, tripping limit switches
• Capacitors in the blower motor section degrade over the idle period and fail under the first sustained load

Annual furnace maintenance in September or October catches all four of these before they cause a furnace not heating call in November. A maintenance visit at $80 to $200 addresses every component on this list.

Furnace Repair vs. Heat Pump — When the Repair Makes You Reconsider

A furnace not heating call that comes back with a significant repair estimate on a system older than 12 years is often the right moment to evaluate heat pump installation rather than furnace repair. A heat pump replaces both the furnace and the air conditioner in a single system, qualifies for federal IRA tax credits of up to $2,000, and delivers both heating and cooling more efficiently than a gas furnace in Greater LA’s moderate climate. The licensed HVAC contractor provides the repair cost, the replacement furnace cost, and the heat pump installation cost on the same visit when the repair situation warrants it.