Furnace Safeties & Venting
High limits, rollout switches and pressure switches.
Furnace Inducer Motor: Testing, Noises and When It's Really the Pressure Switch
How a furnace draft inducer works, how to test one that won't start, runs noisy or runs but won't prove, and how to tell an inducer problem from a pressure switch or venting problem.
Furnace High Limit Switch Tripping: Causes and How to Fix It
Why a furnace's high limit opens, how to confirm it with temperature rise and static pressure, and when the switch itself is the problem.
Furnace Pressure Switch Troubleshooting: Open, Stuck Closed and Dropping Out
Diagnose furnace pressure switch codes by measuring the inducer's draft with a manometer and checking vent, intake, hose, condensate trap and switch.
Furnace Flame Rollout Switch Tripped: What It Means and What to Check
What a tripped flame rollout switch means, why you should not just reset it, and how to check the vent, burners and heat exchanger.