Lone Star Cooling and Heating
Get help with Furnace Ignition Repair
Call Lone Star Cooling and Heating, have us call you, or describe the issue.
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Call (325) 219-0005Gas furnaces that will not light, or light and then shut down, traced through the igniter, flame sensor, pilot assembly and pressure switch to the step of the lighting sequence that is failing.
01Ignition problems
Where in the lighting sequence the furnace stops is the best clue to which part has failed.
The inducer fan runs and the furnace goes through its routine, but no flame appears. A cracked or worn-out igniter, a pressure switch that will not close, or a gas valve that never opens are the usual causes.
Flames appear for a few seconds and then vanish. The control board shuts the gas off when it cannot confirm a flame, and a coated or dirty flame sensor is the most common reason it cannot. Cleaning or replacing the sensor usually cures it.
After a set number of failed attempts the control board locks the furnace out and stops trying, so unburned gas cannot keep building up. The lockout is protection, and the repair is whatever made those attempts fail.
Older furnaces keep a small standing flame burning all season. When it will not stay lit, a worn thermocouple, a dirty pilot opening or a draft across the burner area is usually the cause, and a technician checks the whole pilot assembly.
A loud ignition means gas collected for a moment before it caught, often because of dirty burners, a weak igniter or a gas pressure problem. Each hard ignition strains the heat exchanger, so the furnace is better left off until it is checked.
02Which pattern
These two patterns sound alike and point at different ends of the sequence.
The furnace is stopping before the gas lights. A technician looks at the igniter, the pressure switch and the inducer that must prove the vent is drawing, and the gas valve and supply. A blocked vent or a cracked igniter is a frequent finding here.
Lighting works, but the furnace cannot hold on to the flame. The flame sensor is the first suspect, followed by its wiring and ground, then the condition of the burners and the flame itself. On older furnaces, a failing thermocouple produces the same result.
Furnace Ignition Repair
Serving Abilene, TX.
03Why it locks out
A furnace that refuses to light is following rules written to keep unburned gas out of the building.
The control board opens the gas valve only after the pressure switch reports that the vent is drawing and the igniter has had time to heat up or spark. It then expects to see a flame almost at once. If the flame sensor does not report one, the gas is shut off again, and after a set number of failed tries the board stops trying altogether.
Older furnaces with a standing pilot work on the same principle through a thermocouple, which holds the gas valve open only while the pilot flame heats it. In every version, the lockout is a symptom rather than the fault. Forcing more attempts only repeats the failure, while finding the worn igniter, dirty sensor or blocked vent ends it.
04In the meantime
None of this lights the furnace. All of it keeps a lighting fault from becoming a safety problem.
Leave the building straight away without switching lights, appliances or the thermostat on or off, and without lighting any flame. Call the gas utility or 911 from outside, away from the building.
If the burners bang or boom as they light, switch the heat off at the thermostat and leave it off until a technician has checked the furnace.
A furnace that has stopped trying to light is protecting the building. Leave the power and gas as they are, and mention the blinking light pattern when calling.
05Questions
Most often the flame sensor, a thin metal rod that sits in the flame, has built up a coating that weakens its signal. The control board cannot confirm the flame and closes the gas valve as a precaution. If a clean sensor does not solve it, the wiring, the ground connection and the flame itself are checked next.
It is better not to. Each forced restart gives the furnace more attempts at a step that is already failing, and with some faults that means more gas released before a flame catches. The lockout is there to prevent exactly that, and it is safer left in place until the cause is found.
It is a small ceramic element that glows hot enough to light the gas at the burners. The material is brittle and weakens with every heating cycle, and once it cracks it can no longer glow. Replacing it is one of the most common furnace repairs.
What the system is doing, when it started, what the thermostat is set to and what it reads, and whether the outdoor unit is running. The age of the equipment and a photo of its label help a technician arrive prepared.
If it smells of burning, is leaking water, or the outdoor unit is humming without its fan turning, yes: switch it off at the thermostat. A system that runs but does not keep up can usually stay on until it is looked at.
Lone Star Cooling and Heating
Call Lone Star Cooling and Heating, have us call you, or describe the issue.
Prefer to talk?
Call (325) 219-0005