Heating & Cooling Combined Unit: Why won't my furnace turn on?
Check the thermostat to make sure it's set for heat and the temperature setting is high enough to call for heat. Adjust the thermostat if it isn't set properly.
If you have a digital thermostat and it doesn't light up, check the house circuit breaker for your furnace. Reset the house circuit breaker if it's tripped.
If the thermostat is getting power but won't light up, the thermostat may have failed. Replace the thermostat if it doesn't light up even though it's getting power.
Many furnaces have a power cut-off switch located next to the furnace that shuts off power to the furnace during the off-season. Check that switch to make sure it's turned on.
Other problems that can prevent your furnace from working include: failed interlock switches, exhaust ventilation system problems, wiring failures or control problems. Have a service technician diagnose and repair the furnace failure if you can't fix the problem using basic troubleshooting steps.
THESE REPAIRS MAY HELP SOLVE YOUR HEATING & COOLING COMBINED UNIT PROBLEM
Replace the HVAC system thermostat
The thermostat controls the heating and cooling system in your home. The thermostat senses the temperature inside your home and cycles the system on and off to maintain the set temperature. When your HVAC system control thermostat quits working, replace the thermostat.
Hvac system thermostat
How to replace a heating and air conditioning system thermostat
If the buttons on your HVAC system control thermostat don't work or if the display panel doesn't light up, the thermostat may need to be replaced. This DIY repair guide explains how to replace a thermostat in less than 30 minutes.
Symptoms common to all heating & cooling combined units
Choose a symptom to see related heating and air conditioning system repairs.
Thermostat problem, clogged air filter, burner failure…
Dirty air filter, clogged condenser coils, low refrigerant charge, faulty compressor…
Thermostat problems, bad compressor/condenser fan capacitor, lack of refrigerant, failed compressor…
Main causes: errant thermostat settings, lack of electrical power, clogged drain line, wiring failure, control failure.…
Main causes: Errant thermostat settings, lack of power, bad interlock switches, lack of exhaust ventilation, wiring fail…
Dirty flame sensor, failed flame sensor, damaged burner, bad high limit switch…
Repair guides common to all heating & cooling combined units
These step-by-step repair guides will help you safely fix what’s broken on your HVAC system.
How to unclog the air conditioner drain line
The condensate drain line for your central air conditioner can clog with mold and mildew. Water will back up and start d…
How to replace the furnace flame sensor
The flame sensor detects when furnace burner flames are lit. You may need to replace the flame sensor if flames only sta…
How to replace a heating and air conditioning system thermostat
The control thermostat for your HVAC system can stop working. This repair guide shows how to replace it.…
Articles and videos common to all heating & cooling combined units
Use the advice and tips in these articles and videos to get the most out of your HVAC system.
Learn how to maintain your central air conditioner to keep it running smoothly all summer long.…
Get tips to help keep your central AC running all summer long…
Get answers to frequently asked questions about Sears and Sears PartsDirect.…