Field tools and diagnostic guides for working techs.
Diagnostic Tools
Pick a Symptom
Route from a customer complaint to the right diagnostic flow in two taps.
Open tool →Fault Code Lookup
Decode flash codes and LED patterns — 735 codes across 7 brand families.
Open tool →Diagnostic Guides
Detailed field diagnostic articles for common symptoms.
Why Is My Furnace Blowing Cold Air?Burner lights but supply air is coolWhy Does My Furnace Keep Turning On and Off?Short cycling patterns and root causesWhy Is My Furnace Not Turning On?No ignition, nothing happensWhy Is My Furnace Leaking Water?Water near the furnace on 80% or 90%+Why Is My AC Not Blowing Cold Air?Blower runs, air is warmWhy Is My Furnace Making Strange Noises?Seven shutdown-worthy noises