Orange County winters are usually comfortable, but our mornings and evenings still get cold enough for heaters to run longer. If your furnace is struggling, it often starts with a small issue that snowballs into poor comfort, higher bills, or a no-heat call. Below are the most common furnace problems our technicians see in Orange County homes and what to watch for.
1) Dirty or wrong air filter
A clogged filter restricts airflow, which can cause overheating, frequent shutoffs (short cycling), and weak airflow at vents. Some filters also restrict airflow too much for certain systems.
Signs: weak airflow, dusty vents, frequent cycling, or a furnace that shuts off quickly.
Tip: Check your filter monthly during winter and replace it as needed.
2) Igniter failure
Many modern furnaces use a hot surface igniter. When it fails, you might hear the system try to start, but it never lights.
Signs: clicking, trying to start, then stopping with no heat.
3) Dirty or failing flame sensor
A dirty flame sensor can cause the burner to light briefly and then shut off as a safety response.
Signs: furnace lights, then turns off within seconds or minutes.
4) Thermostat issues
This can be as simple as wrong mode settings or low batteries, or it can be a thermostat that is misreading temperature or failing.
Signs: heat does not turn on, system runs at odd times, or temperature does not match comfort in the home.
5) Blower motor or capacitor problems
The blower moves warm air through your ducts. If the motor or capacitor is failing, airflow can be weak or stop entirely.
Signs: you hear the furnace running but little to no air at vents, or airflow is inconsistent.
6) Duct and return air problems
Blocked returns, closed registers, or duct leaks can make rooms feel uneven and force longer run times.
Signs: one room is cold, another is warm, or airflow is weak in certain areas.
7) Safety switch shutdowns and overheating
Furnaces have safety switches that shut the system down when it overheats or when venting is not right.
Signs: furnace starts then shuts down, burning smell, or repeated cycling.
Quick checks before you call
Confirm the thermostat is on Heat and the set temperature is higher than room temp
Replace the air filter if it looks dirty
Make sure return vents are not blocked
Check the breaker switch for the furnace
Listen for odd noises (rattling, buzzing, repeated clicking)
If the furnace is still not heating, or you smell gas, turn the system off and call for service.
Need furnace help in Orange County?
If your heater is not keeping up, is cycling frequently, or you have no heat, Air Care Heating and Air Conditioning can help. We serve homes across Orange County, including Rancho Santa Margarita, Mission Viejo, Lake Forest, Irvine, and surrounding areas.
Call 949-482-2911 to schedule service.