Frequently asked questions
Why is my furnace running but not heating?
The most common causes are a dirty flame sensor that shuts the burners off, a failed ignitor, a tripped high-limit switch from a clogged filter, or the thermostat fan set to ON instead of AUTO. A technician confirms which one by watching the ignition sequence.
Is it safe to keep resetting my furnace?
No. Repeated resets can flood the burners with gas on some models and mask a safety problem. If the furnace locks out more than once, leave it off and have it checked.
How long does a typical furnace repair take?
Most single-part repairs, such as an ignitor, flame sensor, capacitor or limit switch, take one to two hours once the technician is on site. Inducer motors, control boards and gas valves can take longer if the part has to be ordered.
Can a furnace cause carbon monoxide poisoning?
Yes. A cracked heat exchanger, blocked flue or poor combustion can release carbon monoxide. Keep working CO alarms on every level, and if one sounds, leave the home and call 911 or your gas utility.
What do the blinking lights on my furnace mean?
Most modern furnaces flash a diagnostic code on the control board. The code chart is usually printed inside the blower door. Note the pattern before you call; it speeds up the diagnosis.
Should I repair or replace an old furnace?
If the furnace is under about 15 years old and the problem is a single part, repair is usually the better value. A cracked heat exchanger, an older unit with repeated failures, or very high bills are the main reasons to replace. See the furnace repair cost guide.
How often should a furnace filter be changed in winter?
Check it monthly during heating season. One-inch filters often need replacing every one to three months; thicker media filters last longer. A clogged filter is a leading cause of overheating and short cycling.
Do you cover my town?
Our referral network covers all 50 states and DC. Find your state on the coverage map or just call; the line routes to a provider who serves your ZIP code.
Do you do the repair yourselves?
No. Emberline is a referral service. We connect you with an independent licensed HVAC provider, who quotes and performs the work. See how it works.
What should I do if I smell gas near the furnace?
Do not touch light switches or the thermostat. Leave the house, then call your gas utility or 911 from outside. A furnace repair call comes after the leak is made safe.