Furnace Not Turning On
Furnace completely unresponsive with no sounds, no ignition attempt, or no blower activation.
Emergency Situation
This is a serious problem that requires immediate attention. If you smell gas, see smoke, or notice electrical sparking, shut off your system immediately and call a professional or emergency services.
Quick Overview
DIY: 15-30 minutes | Professional: 1-2 hours | Control board: 2-4 hours
Winter
Common Symptoms
You might be experiencing this problem if you notice any of these signs:
- No response when thermostat adjusted
- Complete silence from furnace
- No blower or igniter sounds
- Thermostat display blank
- Indicator lights off on furnace
- No clicking from igniter
- Circuit breaker tripped
- Reset button popped on furnace
Step-by-Step Diagnosis
Follow these steps to identify the exact cause of your problem:
- Check thermostat display for power
- Replace thermostat batteries if display dim/blank
- Verify thermostat set to HEAT mode
- Check main electrical panel for tripped breakers
- Look for furnace power switch near unit
- Check for blown fuses in furnace
- Locate reset button on furnace - note if popped
- Verify gas valve is open (handle parallel to pipe)
- Listen for any sounds when thermostat calls for heat
- Check door safety switch on furnace panel
- Look for error codes on furnace display
- Verify exhaust and intake vents are clear
Most Common Causes (Ranked by Likelihood)
Tripped circuit breaker
HIGH LIKELIHOODFurnace power switch off
HIGH LIKELIHOODDead thermostat batteries
HIGH LIKELIHOODDoor safety switch not engaged
MEDIUM LIKELIHOODBlown fuse in furnace control board
MEDIUM LIKELIHOODFailed transformer
LOW LIKELIHOODControl board failure
LOW LIKELIHOODPressure switch stuck or failed
LOW LIKELIHOODDIY Solutions
What You'll Need:
- Replacement batteries
- Flashlight
- Screwdriver
- Replacement fuses (3 amp automotive type)
Time Required: 15-30 minutes
Step-by-Step Instructions:
- Replace thermostat batteries
- Check electrical panel - reset tripped breaker
- Locate furnace power switch (looks like light switch)
- Flip power switch OFF then ON
- Ensure furnace access door is fully closed and latched
- Press door panel firmly - safety switch must click
- Check for and replace blown fuses on control board
- Verify gas valve handle is parallel with pipe
- Wait 3-5 minutes after power restoration
- Set thermostat 5 degrees above room temp
- Listen for igniter clicking or blower starting
- Record any error codes from furnace display
⚠️ Safety Warnings
- If you smell gas, leave immediately and call gas company - don't flip switches
- Never reset a breaker more than once
- Don't bypass safety switches
- If reset button trips repeatedly, call professional
When to Call a Professional
Don't attempt DIY repairs if you experience any of these situations:
- Gas odor near furnace
- Breaker trips repeatedly
- No power to furnace with good breakers
- Error codes displayed
- Recent power surge or lightning
- Burning smell from furnace
- Furnace is more than 15 years old
- Reset button keeps popping
- Previous DIY repairs didn't help
Prevention Tips
Stop this problem before it starts with these preventive measures:
- Test furnace in early fall
- Replace thermostat batteries annually
- Label furnace breaker clearly
- Keep furnace area clear and accessible
- Install whole-home surge protector
- Schedule annual pre-season inspection
- Know location of all safety switches
Frequently Asked Questions
Where is the reset button on my furnace?
The reset button is typically a small red or yellow button on the furnace burner assembly or control panel. It pops out when the furnace overheats. Push it in to reset. If it pops again within an hour, shut down the furnace and call a professional - repeated resets indicate a serious problem.
Why does my furnace breaker keep tripping?
Repeated breaker trips indicate electrical problems like a failing blower motor drawing too much current, short circuit in wiring, or failed control board. Never keep resetting the breaker - this is a fire hazard. Call an HVAC technician to diagnose the electrical issue.
How do I know if my furnace control board is bad?
Signs include: no lights on furnace, error codes, furnace won't respond to thermostat, clicking without ignition, or burning smell from furnace. Control boards can fail from power surges, age, or moisture. Replacement costs $300-800 including labor.
Related Problems
Furnace Not Heating
Furnace runs but produces no heat, or blows cold air instead of warm air.
Thermostat Problems
Thermostat display issues, unresponsive controls, incorrect temperatures, or HVAC not responding to settings.
Furnace Short Cycling
Furnace starts and stops in short bursts instead of running full heating cycles.