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.