Furnace Repair

In most North Texas homes, the furnace is never fully off, even though it only makes heat for a few months. The same cabinet in the attic or hallway closet holds the blower that moves your air conditioning, so its motor and control board work through every summer, often in an attic far hotter than the rooms below. The burners, igniter, and safety switches, meanwhile, sit unused until a cold front or an ice storm asks them to run for hours.

W3 Electric Heating & A/C repairs furnaces throughout Rowlett, Rockwall, McKinney, Garland, Wylie, Forney, and the rest of the Dallas area, and emergency calls reach us 24 hours a day. A furnace is as much an electrical appliance as a gas one: a control board decides every step, and an electric furnace is one of the largest electrical loads in the house. Holding both HVAC and electrical licenses lets us follow a fault from the burners back to the breaker.

Furnace repair is a diagnostic visit focused on the furnace itself: a gas or electric unit that will not start, lights and then shuts down, blows cool air, trips a breaker, or flashes an error code. Because we know the equipment, we can go straight to its startup sequence.

If you are not sure what kind of system you have, our general heating repair page covers every type. If your furnace runs well and you want it checked before winter, book a heating tune up instead. This page is for a furnace that is misbehaving now.

Every modern gas furnace starts the same way. The thermostat calls for heat, the inducer motor clears the vent, a pressure switch confirms the draft, the hot surface igniter glows, the gas valve opens, the flame sensor proves the burners lit, and only then does the blower start. The step that stalled tells us which part to test.

The inducer is a small fan that pulls combustion gases through the furnace and out the vent before the burners light. When its bearings wear, it hums, rattles, or never reaches speed, and the pressure switch never closes. The switch can also stay open because the vent is blocked, a rubber hose has cracked or filled with water, or a condensate trap is clogged. The furnace treats each of these as unsafe and will not light. Replacing the switch without finding out why it stayed open rarely holds.

Hot surface igniters are brittle, and a cracked one simply stops glowing. When the burners light for a few seconds and then go out, the flame sensor is the usual suspect: a thin film of residue keeps it from sending the faint signal that proves a flame is present, so the control board closes the gas valve as a precaution. A gas valve that will not open is less common, and we confirm it with a meter before replacing anything. None of these parts are safe for homeowners to work on.

The control board runs the whole sequence and keeps track of what went wrong. Many furnaces report it with a blinking light visible through a small window in the lower door, and a label on the door explains each pattern. Write the pattern down before anyone turns the power off, because a power cycle often clears it. Boards fail from attic heat, power surges, and shorted wiring, and a board ruined by a wiring fault will fail again. We find the short first, so you only buy one board.

A high limit switch turns the burners off when the furnace overheats inside, almost always because air is not moving through it: a clogged filter, blocked returns, a weak blower, or a dirty AC coil. If filters keep clogging quickly, better air filtration can help. A rollout switch is more serious. It trips when flame escapes the burner area, which can point to a blocked vent or heat exchanger. We never bypass either switch, and we will not reset a tripped rollout switch and leave without finding the cause.

A high-efficiency furnace pulls so much heat from its exhaust that water condenses inside it, and that water leaves through a trap, a drain line, and sometimes a small pump. When the trap clogs, the pump fails, or the line sags or freezes, water backs up, the pressure switch cannot close, and the furnace locks out. A drain run through a cold attic or an outside wall can freeze during a hard North Texas freeze. White plastic vent pipes on the furnace tell you that you have this type.

Homes without a gas line often heat with an electric furnace: heating elements in the air handler, switched on in stages by sequencers or relays. When an element burns out or a sequencer fails, you get weak heat, uneven heat, or none, and a sequencer stuck closed can keep an element on when it should be off. These circuits carry heavy current, so loose and overheated connections are common and a genuine fire concern. We test the elements, sequencers, breakers, and wiring together.