Heater not working? Test it before the first cold night

Houston heating fails in a specific and predictable way, and it has almost nothing to do with how cold it gets. Your system sits untouched for ten months, then gets asked to run hard on the handful of nights a year that it matters. The idle time is the problem, not the cold.

The useful thing about that is it makes the failure preventable. You just have to find it in September or October instead of at 2am in December.

The single most common no-heat call

A furnace that worked fine last winter and now lights, runs for a few seconds, then shuts off. It may repeat that two or three times before locking out entirely.

That is usually a dirty flame sensor. It is a thin metal rod that sits in the burner flame and confirms to the control board that the furnace actually ignited. Over a long idle summer it picks up a film of oxidation and dust. Once it can no longer sense the flame, the board assumes ignition failed and shuts the gas off exactly as designed. Nothing is broken. The safety is doing its job on bad information.

It is a clean, not a replacement, and it is one of the least expensive visits we run.

What else goes wrong after a long summer

• Cracked or failed ignitor. These are brittle and fail with age. You call for heat, the inducer runs, and nothing lights.
• Dust on the burners, which makes ignition rough and uneven.
• Rodent and insect damage. A furnace cabinet is a warm dry place to spend a summer. We find chewed wiring and nests more often than people expect.
• Seized inducer or blower motors that have not turned since February.
• Dead thermostat batteries, which is a genuinely common cause of no heat and costs nothing to rule out.
• A tripped condensate safety. High-efficiency furnaces produce condensate, and a drain that clogged over the summer will lock the furnace out.

The burning smell, and when to worry

A faint burning smell on the first run of the season is normal. It is dust burning off the heat exchanger and it should clear within ten or fifteen minutes.

What is not normal:

• A smell still there after twenty minutes, or one that returns on every cycle.
• Anything that smells like hot plastic or melting electrical insulation.
• Visible smoke, or soot around the furnace or the registers.

Shut the system off and call someone for any of those.

Carbon monoxide is why gas heat gets a safety check

A furnace burns gas, and the heat exchanger is the metal wall keeping combustion gases separate from the air blowing into your house. When that metal cracks with age and thermal cycling, combustion byproducts including carbon monoxide can get into the supply air.

Carbon monoxide has no smell and no color. Early symptoms look like flu: headache, dizziness, nausea, fatigue. The telling detail is that they often ease when you leave the house and come back when you return. If your household notices that pattern in winter, get outside and get medical help before you call an HVAC company.

Two things follow. Put a working CO detector on every sleeping level, because it is inexpensive and it is the only thing that actually detects this. And make sure any heating inspection includes checking the heat exchanger and confirming the flue is drafting. If we find a cracked exchanger we will tell you plainly and shut the system down. That is not something you run through the winter and deal with in spring.

Heat pumps fail differently

Plenty of Houston homes run heat pumps, which makes sense here because our winters are mild and the same equipment cools you all summer. No burners means the gas concerns above do not apply. What goes wrong instead:

• The reversing valve sticks. That is the part that flips the system from cooling to heating. When it fails you get air conditioning when you asked for heat, which is a memorable way to discover the problem in December.
• Auxiliary strips carrying the whole load. If your backup electric heat runs constantly on a 45 degree night, the heat pump is not doing its job. You will see that on the electric bill before you feel it in the house.
• Defrost failures. A heat pump ices its outdoor coil in cold damp weather and is supposed to reverse briefly to melt it clear. A failed defrost board leaves the unit buried in ice and unable to make heat.

The fifteen minute test, worth doing this month

Pick a mild day. This costs nothing and takes almost no time.

• Put a fresh filter in first, so you are not testing through a summer of dust.
• Set the thermostat to HEAT and push the target about five degrees above the room.
• Let it run fifteen minutes. Expect a faint dust smell that clears.
• Check that air at the registers is actually warm, not just moving.
• Listen for grinding, squealing, or repeated clicking without ignition.
• Look at the furnace itself for water, rust, or soot.
• Test your CO detectors and change the batteries while you are thinking about it.
• Set the thermostat back to normal.

If something is wrong, you have found it in September with weeks to spare, instead of during the week when every HVAC company in Houston is booked solid.

Why the freeze week is the wrong time to find out

Houston gets a hard freeze rarely enough that most homes here are not ready for one, and when it lands the whole city needs heat on the same night. Supply houses run out of common parts. Every reputable company is triaging. The people who get served fastest are the ones whose problem was already known and already scheduled.

It is the same argument as booking an AC tune-up in March instead of June, which we make in our Houston maintenance checklist. The heating version just has a shorter and less forgiving window.

When to stop and call

• Any smell of gas. Leave first, call from outside.
• A burning smell that persists past the first cycle.
• The furnace tries to light repeatedly and locks out.
• The breaker trips when the heat runs. That is an electrical fault, not a reset.
• A CO detector sounds. Get everyone outside first.
• Warm air never arrives, or arrives only from the backup strips.

We service furnaces, heat pumps and electric strip heat across Houston, and we answer 24 hours, because the first cold night does not check the clock. More on that on our heating and furnace repair page.