AC Not Cooling? A Maintenance Tech's Step-by-Step Diagnostic Flow

AC running but not cooling is one of the most common summer calls. Here's how to work through the 5 most likely causes in order — so you don't waste time replacing parts that aren't the problem.

Furnace Not Igniting? A Field Tech's Step-by-Step Diagnostic Flow

Furnace clicks but won't light? Here's how to diagnose the 5 most common causes in order — bad ignitor, dirty flame sensor, gas supply issue, pressure switch fault, or a locked-out control board.

Water Heater Pilot Light Won't Stay Lit? A Field Tech's Diagnostic Flow

Pilot keeps going out? The thermocouple is the culprit 80% of the time. Here's how to diagnose and fix a water heater pilot that won't hold — thermocouple test, pilot cleaning, draft check, and gas valve diagnosis.

Garbage Disposal Humming But Not Working? A Field Tech's Diagnostic Flow

Disposal hums but won't spin? Almost always a jammed flywheel. Here's how to clear it with a hex wrench, press the reset, and diagnose what to do if it still won't start — with notes for InSinkErator, Waste King, Moen, and KitchenAid.

Thermostat Not Working? Blank Screen Diagnostic Flow for Field Techs

Thermostat screen completely blank? It's a power problem — breaker, fuse, C-wire, or transformer. Here's the 6-step diagnostic flow with manufacturer-specific notes for Nest, Ecobee, Honeywell Home, and Emerson Sensi.