Heating and air conditioning system repair guides

When your HVAC system goes out, you'll want to fix it fast so you're not miserable inside your home. These step-by-step repair guides show you how to complete common repairs such as clearing a condensate drain line or installing a new control thermostat. And we have more helpful information on our heating and air conditioning repair help page, like symptoms and solutions for top HVAC brands such as Kenmore, Carrier and Lennox. Search your model number to find a complete list of replacement parts, then order the part you need.

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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.

March 16, 2022
By Lyle Weischwill
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 dripping below the inside air conditioner unit. Follow the steps in this guide to unclog the drain pipe.

Repair difficulty
Time required
15 minutes or less
March 16, 2022
By Lyle Weischwill
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 stay on for a few seconds.

Repair difficulty
Time required
15 minutes or less
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.

Repair difficulty
Time required
30 minutes or less

Symptoms common to all heating & cooling combined units

Choose a symptom to see related heating and air conditioning system repairs.

Dirty air filter, clogged condenser coils, low refrigerant charge, faulty compressor
Thermostat problem, clogged air filter, burner failure
Dirty flame sensor, failed flame sensor, damaged burner, bad high limit switch
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 failures.

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.

August 30, 2022

How to enjoy all the online benefits we offer on our Sears PartsDirect website

By Lyle Weischwill

Learn about all the convenient features on our Sears PartsDirect website that make your parts purchases easier.

August 5, 2022

Introducing new technical repair content that we’re developing for the Sears Technical Institute

By Lyle Weischwill

Learn about Sears Technical Institute and the advanced technical content being developed for aspiring appliance techs.

February 22, 2022

Can a furnace be repaired?

By Lyle Weischwill

Learn about furnace repairs and how much they cost.