What's it doing?
Start from the symptom, not the part number. Pick what your system is doing and we'll rank the most likely parts from thousands of real repairs — and tell you the free fix to try first, before you buy anything.
Why start from the symptom
The same symptom points at completely different parts depending on your equipment — a furnace that won't light and a heat pump stuck in defrost share nothing but the cold house. So we ask what you have first, then rank the likely parts by how often each one is the actual fix.
Every ranking leads with the free check to run before you spend a cent. If the honest answer is "clean it, don't replace it," that's what it says.