Gas Furnace Running But Not Heating? Fix It Now
When our gas furnace turns on but fails to blow hot air, it's frustrating. But don't panic. In most cases, some DIY troubleshooting can get heat restored fast.
We'll walk through the leading culprits behind furnaces that run without heating homes. By methodically checking each possibility, you can often diagnose and fix the issue on your own.
Ensure Gas Supply and Check for Leaks
Before anything else, we must check gas levels and test for leaks. Start by ensuring the gas valve leading to your furnace is turned to the open position. Then examine the gas line for any visible damage or obstructions. Soap and water can also detect leaks quickly. Apply it around joints and connections, looking for bubbles.
If leaks are spotted? Evacuate immediately and call emergency services. Gas leaks can rapidly cause carbon monoxide poisoning or even explosions.
Warning Signs of Gas Leaks
- Rotten egg smell
- Hissing or whistling noise
- Dead plants near gas appliances
- Dirt or debris blowing from pipelines
- Bubbles around joints and connections
Examine Thermostat Settings and Operation
Next, ensure your thermostat settings aren't preventing heating. Verify it's set to "heat" mode and the temperature is raised above room level. If so, test if the thermostat properly calls for heat. Switch settings to call for a fan, checking if the blower activates. If only the blower works, it likely indicates a faulty thermostat.
How To Test a Faulty Thermostat
With the cover removed, use a multimeter to check if the thermostat receives continuous low-voltage power. If not, there may be wiring issues. If it receives power, the internal switch is likely bad. Replacing modern digital thermostats is straightforward. Analog versions can often be repaired by bending contacts back into place.
Inspect Power Supply and Electrical Components
Now check your electricals. Verify the furnace switch near your unit is turned on and no fuses/breakers have tripped. If they quickly trip again after resetting, it could signify shorted wiring or a bad motor/control board.
Use a multimeter to test voltage to the gas valve and ignitor. If absent, faulty internal wiring may be preventing ignition. If everything receives power, ignitors or control boards themselves may need replacement.
Warning Signs of Electrical Issues
- Frequently tripped fuses or breakers
- Scorch marks or burning smells from unit
- No power light on furnace
Check Ignition System and Burners
The pilot light and ignitor kickstart combustion inside the furnace. But issues can prevent ignition. Examine your pilot light assembly for any dirt buildup or damage blocking the gas flow. Remove debris carefully using compressed air. Verify wires to ignitors aren't damaged or corroded.
Next, check the burners themselves. Use a soft brush to dislodge any dirt or debris preventing gas from flowing and igniting properly. If severely blocked, specialized cleaning wands for furnaces can help. Damaged burners may need replacement.
How To Clean Furnace Burners
- Switch furnace power OFF
- Remove outer cabinet panel
- Brush burners gently with soft-bristle attachment
- Use compressed air to dislodge stubborn debris
- Examine burners and replace if damaged
Evaluate Flame Sensor Function
Flame sensors confirm ignition occurred inside the furnace. If unable to detect a flame, gas flow ceases as a safety measure. But dirty or cracked sensors can trigger false alarms. Carefully clean any soot deposits off using an emery cloth. Avoid bending or damaging rods.
If cleaning doesn't help, replacement may be required. Sensors screw into the burner assembly, making DIY installation straightforward.
Flame Sensor Troubleshooting
- Remove power to furnace
- Detach and clean sensor gently with emery cloth
- Reattach tightly into burner housing
- Restore power and test operation
- Replace sensor if issues persist
Examine Blower Function and Airflow Path
Your blower circulates heated air through ductwork into rooms. But blower issues can reduce efficiency. Inspect fan blades and motors for any dirt accumulation, damage, or noises/vibration. Clean gently using compressed air.
Blockages in ducts, registers, and filters also lower airflow. Check for kinks in ductwork or buildup limiting capacity. Clean or replace air filters if dirty. Opening stuck registers can also help.
Improving Furnace Airflow
- Clear debris from blower fan and compartment
- Eliminate kinks/clogs in ductwork
- Clean or replace dirty air filters
- Open any closed vents/registers fully
Assess Heat Exchanger Condition
Cracks or holes in the heat exchanger lower efficiency and release combustion byproducts inside the home. Carefully inspect your heat exchanger for damage or corrosion with a flashlight. Look for cracks, leaks, or separations.
If the exchanger shows substantial damage? Replacement is required. Attempts at patching small leaks often fail quickly in the high-heat environment.
Signs Your Heat Exchanger Needs Replacement
- Visibly cracked or damaged
- Corroded areas or holes
- Carbon soot stains around cracks
- Gas smells in the home
Utilize Professional Assistance When Needed
In some cases, underlying issues may prove complex for DIY troubleshooting and repair. If you smell gas, suspect carbon monoxide, or lack experience with household electrical - immediately contact HVAC professionals instead of attempting repairs yourself.
Technicians have specialized tools and knowledge for accurately diagnosing furnace problems. They can also advise if full replacement is ultimately more cost-effective than continuing repairs on an aging unit.
It's also wise having professionals perform annual tune-ups and cleaning. Preventative maintenance often catches small issues early - before they cascade into complete furnace failures on cold nights.
Don't endure bone-chilling temperatures if your gas furnace fails to heat properly. In many cases, there are accessible solutions for owners able to methodically troubleshoot common issues. Ensure gas and power supplies first before moving to ignition systems, burner cleaning, and airflow paths.
We hope these tips help restore welcoming warmth on demand. But with any gas malfunctions or leaks - always err on the side of safety. Modern heating systems prove overwhelmingly reliable when properly maintained, keeping homes toasty for years.