Heat Not Working? Furnace & Heat-Pump Troubleshooting

Waking up to a cold house when a freeze is in the forecast is no fun. Before you assume the worst, know that many "no heat" calls in the Leander area come down to a thermostat setting, a tripped breaker, or a dirty filter — things you can rule out in a few minutes. This guide walks the safe checks first, then the problems that genuinely need a licensed technician, with a clear line on the gas-safety steps you should never attempt.

First, what "no heat" usually means

A heating system that won't heat is failing at one of a few jobs: it's not getting the signal to run, not getting power, not igniting (gas) or reversing (heat pump), or it's locked out on a safety. Narrowing it down tells you whether this is a five-minute fix or a real repair.

Safe checks you can do yourself

None of these involve tools or opening sealed equipment. If one fixes it, you've saved a call:

1. Thermostat
   Set to Heat, temperature above the current room temp, fan on Auto (not “On”), and batteries fresh.
2. Breaker & power switch
   Check the furnace breaker, and the furnace power switch on or near the unit — it looks like a regular light switch.
3. Filter
   A badly clogged filter can choke airflow enough to trip a safety. Swap a gray one.
4. Furnace door panel
   If it isn't fully latched, a safety interlock keeps the furnace off on purpose.
5. Vents and registers
   Make sure your supplies and returns are open and unblocked.

STOP — gas-safety lines you should never cross

Combustion and gas work belongs to licensed, certified technicians — full stop. See Gas Furnace Basics for the safety parts that matter.

When it's a pro call

• Furnace blows cold air after the checks above — likely a failed ignitor or flame sensor.
• It clicks/tries to start, then shuts off — a safety lockout that needs diagnosis.
• A heat pump runs constantly on "aux heat" in mild weather — see heat pumps explained.
• Yellow flame, soot, banging, or any gas smell — stop and call.

How MLD handles no-heat calls

We prioritize safety and speed when your heat is down. Our NATE- and EPA-certified, York Factory-Authorized technicians (license TACLA37761C) diagnose the actual cause, check combustion and safeties, show you what failed, and quote a flat rate before any work. We've kept Leander, Cedar Park, Georgetown, Liberty Hill, and Round Rock homes warm since 2009 — with same-day and after-hours help when the cold hits.

What to do next

• Heat completely out and freezing weather? See Emergency & After-Hours Help.
• Prepping for winter? Use the Central Texas winter prep checklist.
• Got a repair quote elsewhere? Get a free second opinion.

Or call 512-528-4258. We'll get your heat back on safely.