Why Is My Heater Not Working?
When your heater won't work, start with the basics: check thermostat batteries and settings, then check the circuit breaker. A dirty air filter can also cause shutdown. If your gas furnace won't ignite, the pilot light may be out or the igniter may have failed. Most heating issues in Phoenix happen on the first cold day because systems sit idle for months.
Common Causes
Thermostat Issues
The thermostat may have dead batteries, be set incorrectly, or be malfunctioning. This is the most common and easiest issue to fix, always check here first.
Tripped Circuit Breaker
Your heating system has a dedicated breaker that can trip due to power surges or electrical issues. Check your electrical panel for a tripped breaker.
Pilot Light Out (Gas Furnace)
If you have a gas furnace with a standing pilot light, it may have gone out. Modern furnaces use electronic ignition, but older units still use pilot lights.
Dirty Air Filter
A severely clogged filter restricts airflow and can cause the system to overheat and shut down via the limit switch. This is a common cause of intermittent operation.
Ignition Failure
Modern furnaces use electronic ignition (hot surface igniter or spark ignition). These components wear out and can prevent the furnace from lighting.
Safety Switch Triggered
Furnaces have safety switches that shut down the system if something's wrong, overheating, flame rollout, or pressure issues. These require professional diagnosis.
What Should You Do?
Try This First
- Check thermostat batteries and settings, ensure it's set to HEAT
- Verify the temperature is set higher than current room temperature
- Check the circuit breaker for your furnace/heating system
- Check and replace the air filter if dirty
- Make sure all supply vents are open and unobstructed
Call a Pro If...
- The breaker keeps tripping after reset
- You smell gas near your furnace (leave immediately, call 911)
- The furnace makes clicking sounds but won't ignite
- You see a flashing error code on the furnace
- The blower runs but no heat comes out
- You've checked obvious issues with no improvement