When a Goodman furnace won’t ignite, start with power, thermostat, filter, and the control board’s light, then trace gas, venting, and flame sensing.
When a gas heater stalls at startup, the chain of safeties has broken somewhere. This guide gives a clean, step-by-step path to find the snag, explain what each part does, and show what’s safe for a handy owner versus what calls for a licensed tech. You’ll see plain checks first, then deeper items. If you smell a rotten-egg odor, leave the space and call your gas utility from outdoors.
Quick Checks Before You Dig Into Parts
Start with the items that most often stop ignition and take seconds to review. These checks restore heat in many homes without tools.
| Symptom Or Clue | Likely Cause | Action |
|---|---|---|
| No blower, no clicks | Power off, tripped breaker, door switch open | Reset breaker, seat access panel, confirm switch |
| Thermostat says heat, furnace idle | Call for heat not reaching board | Set to Heat, raise setpoint, replace weak batteries |
| Inducer starts, no flame | Ignitor cracked, gas off, pressure switch stuck | Watch ignitor glow, verify gas valve position, inspect tubing |
| Flame lights, drops in seconds | Dirty flame sensor | Clean sensor with fine abrasive; reinstall |
| Rapid starts and stops | Clogged filter or registers, limit opening | Install fresh filter, open returns and supplies |
| LED flashes a code | Board lockout or safety open | Note flash count, match to model code chart |
Read The Status Light And What It Tells You
Your control board blinks a pattern to report faults. Count the flashes, match the number to the chart for your exact model, and you’ll know where to aim next. Many boards use patterns that point to ignition retries, pressure switch faults, open limits, or a loose door switch. Models differ, so use the chart in your manual or the manufacturer’s online lookup for the best match to your board’s logic. You can search codes by model with the Goodman fault-code tool, which mirrors the tables on the blower-door label.
Goodman Heater Not Igniting: Likely Causes
Ignition takes a sequence: call for heat, induced draft, pressure switch proves airflow, hot surface ignitor glows, gas valve opens, flame sensor reports fire, and the board keeps the gas flowing. A miss anywhere stops the show. The sections below move in that same order so you can test along the path.
Power, Door Switch, And Thermostat
Confirm the switch near the unit is on and the breaker is set. Reseat the blower door so the safety switch closes. At the wall, set Heat and bump the setpoint at least 5°F above room. If the thermostat uses batteries, swap them. Many no-heat calls trace back to a weak battery or a loose door.
Filter And Airflow
A packed filter chokes airflow. The heat rises too fast, the limit switch opens, and the board stops the gas. Slide in a fresh filter with the arrow pointed toward the blower. Make sure returns aren’t blocked and supply registers are open. If the unit short-cycles, airflow is a top suspect.
Inducer And Pressure Switch
At startup the inducer motor clears the heat exchanger and pulls a draft. A small hose sends that draft to the pressure switch. If the tube is cracked, full of water, or off its barb, the switch won’t close and the board won’t light the ignitor. Pinched vent pipes, birds’ nests, long runs, or a sagging condensate hose can starve draft. Gently clear the tube, straighten kinks, and be sure the vent is free.
Hot Surface Ignitor
Silicon-nitride ignitors glow white-hot to light the burners. Hairline cracks stop them from heating. Look for a bright glow during the trial for ignition. No glow points to a failed ignitor, loose plug, bad ground, or a board output issue. Handle only by the plug or bracket; finger oils shorten life.
Gas Supply And Valve
Verify the manual shutoff at the furnace is inline with the pipe. The valve on the gas meter must also be open. If only some appliances work, you may have a supply issue. The gas valve inside the unit receives a 24-volt signal during ignition; a tech can test that safely with a meter and a manometer for inlet and outlet pressure.
Flame Sensor
The sensor sits in the burner flame and sends a tiny current to prove fire. Oxide on the rod insulates it, the board stops gas a second after light-off, and you get repeated tries. Remove power, pull the single screw, and polish the rod with a fine abrasive pad or steel wool. Clean only the rod, not the porcelain. Reinstall and route the lead clear of hot surfaces. This quick step fixes many drop-outs after light-off.
High-Limit And Rollout Switches
These safeties open if heat spikes or flame moves where it shouldn’t. Triggers include a clogged filter, closed registers, failed blower, blocked heat exchanger, or a vent issue. Never reset a rollout without fixing the cause. If a limit trips often, stop and call a pro to check airflow and the exchanger.
Condensate Drain On 90%+ Models
High-efficiency units create water that must drain. A kinked hose, a frozen trap, or a plugged outlet keeps the pressure switch from closing. Clear the hoses, flush the trap, and make sure the outlet isn’t frozen or blocked. If the trap is dry after a long off period, prime it with water so air can’t bypass the draft path.
Step-By-Step: Safe DIY Checks In Order
Work in short steps and test after each move. This saves time and points you to the failed part without guesswork.
- Set the thermostat to Heat, fan Auto, and raise the setpoint.
- Check the breaker and the service switch next to the unit.
- Open the blower door and seat it firmly so the switch closes.
- Install a fresh filter and open all return and supply grilles.
- Watch the startup: inducer on, ignitor glow, gas valve click, flame, blower.
- If flame drops in a second, clean the flame sensor and retry.
- If there’s no glow, inspect the ignitor for cracks or broken wires.
- Read the board’s flashes and match them to your model’s chart or the official online tool.
- Clear the condensate trap and hoses on high-efficiency units.
- If you smell gas, stop, go outside, and call your utility.
Reset And Lockout Behavior
Most boards try to light several times. After repeated failures they enter lockout to keep raw gas from pooling. Many units clear this state after a timed delay; others need a power cycle. If you cycle power, fix the root cause first or the board will land back in lockout with the same code. If the LED calls out a rollout event or a flame sensed out of sequence, do not keep restarting. Call a licensed technician.
Model-Specific Notes And LED Patterns
Two-stage and modulating lines share the same story line but they flag faults with different blink counts. Keep the exact code table for your model handy. The board label or the install manual lists what one blink, two blinks, or a steady light means for that series. Some boards add slow/fast rates to widen the code list. A factory chart beats guesswork every time and aligns with how your board was programmed.
Patterns You’ll See Across Many Models
- One flash: pressure switch issue.
- Two flashes: open limit or rollout chain.
- Three flashes: ignition retries exceeded or lockout.
- Steady light: normal standby with 24V present.
Safety First Every Time
Any time a combustion device misbehaves, treat it with respect. A CO alarm belongs near sleeping areas and by the heater. If a CO alarm sounds, move outside and call emergency services. For plain guidance from health authorities, read the CDC furnace safety fact sheet. If you smell rotten eggs, leave the building without flipping switches or using phones inside; utilities add odorant for this purpose and gas can ignite from a spark. See response steps from the American Gas Association.
Troubleshooting Map From Call For Heat To Flame
Use this condensed map to move from symptom to fix. It follows the ignition order and keeps you from skipping a gate.
| Stage | What To See Or Hear | If Not, Look Here |
|---|---|---|
| Call For Heat | Thermostat click, board LED awake | Thermostat wiring, R-W signal, fuse on board |
| Inducer Starts | Small fan runs, soft whir | Power to inducer, seized bearings, relay on board |
| Pressure Proves | LED changes state | Rubber hose, vent block, switch contacts |
| Ignitor Glows | Bright orange tip lights | Cracked element, loose plug, bad ground |
| Gas Valve Opens | Soft click, flame lights | Manual valve open, 24V at valve, supply pressure |
| Flame Proves | Stays lit past one second | Dirty sensor, poor flame carryover, burner ground |
| Blower Runs | Warm air at registers | Motor run cap, control timing, high-limit cycling |
Thermostat And Low-Voltage Wiring Tips
The call for heat rides the R and W conductors. A loose splice, a pinched cable near the furnace, or a failed fuse on the board can break that call. If the screen goes blank in heat mode only, check the common wire and any add-on devices such as a smart thermostat base or a humidifier tapping the 24-volt circuit. Keep low-voltage wiring clear of the burner box and any moving parts.
Parts, Tools, And Skill Level
Some fixes fit a Saturday skill set, others belong to a shop van. Here’s a plain take so you can plan the right next step.
Owner-Level Items
- Replace the filter and open grilles.
- Clean the flame sensor.
- Seat the blower door and check the door switch.
- Clear condensate tubing and traps on condensing models.
- Power cycle to clear lockout after you fix the cause.
Tech-Only Items
- Ignitor ohm tests and safe replacement without stress on the element.
- Live gas valve diagnostics with meter and manometer.
- Combustion analysis and vent draft tests.
- High-limit and rollout diagnostics tied to airflow or exchanger faults.
- Board replacement and wiring repairs.
Care Tips To Prevent No-Light Problems
Seasonal care keeps the startup chain intact. Swap the filter on a schedule, keep the drain clear, and wipe the flame sensor once a heating season if your model tends to film over. Vacuum around the burner box with power off. Keep storage clear of the heater so service panels open easily. If the vent exits a shaded wall, look for frost in cold snaps and clear it before the next call for heat.
Specs, Manuals, And Where To Find Them
The label inside the blower door lists model and serial. With that ID you can pull the matching manual and product sheet from the brand’s library. The literature lists vent sizing, condensate routing, and service notes that relate to draft and ignition. When you match the model family and board revision, the flash table lines up with what your LED shows during a fault.
When To Call A Licensed Technician
Live gas work, vent testing, and board-level diagnosis need instruments and training. Call a pro when you see melted wiring, repeated lockouts, a scorch mark near burners, water around the base of a condensing model, or any flash code that points to rollout, pressure switch faults that persist, or a control failure. If you changed the filter, cleaned the sensor, checked the door switch, and still can’t keep a flame, scheduling a visit is the safest next step.