The short answer
A Coleman furnace code is the light blinking through the small window in the lower door: count the red flashes and match the number to the chart. In Northern Virginia homes, three come up most: 3 red flashes (the pressure switch never closed, usually a blocked vent, a backed up drain or a tired inducer), 7 red flashes (no flame after three tries: the flame sensor, the igniter or the gas) and 4 red flashes (it overheated, usually a clogged filter). Change the filter, check the vent pipes and the drain, power cycle once, and call if the same count comes back.
Why a Coleman reads like a York
Coleman, York and Luxaire gas furnaces come from the same company. One owner’s manual covers all three names, and Coleman’s modulating CP9C shares its installation manual with York’s YP9C (CP9C manual). So the York flash chart is the Coleman chart. The sticker inside the blower door is the final word for your model.
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How to read the light
Leave the blower door on. Taking it off opens a safety switch, and the light goes out with the power. Look through the clear window low on the door:
- Slow green flash: it has power and nothing’s calling. Normal.
- Slow amber flash: the thermostat is calling for heat and it’s running. Normal.
- Red flashes in a group, a pause, then the group again: a fault. Count it twice.
- A light that stays on without flashing: the control board itself failed.
Coleman furnace flash codes
From the TM9E installation manual, the single-stage furnace in this family; the TM8E prints the same chart.
Swipe to see all columns →
Swipe to see all columns →
| Light | What it means |
|---|---|
| Slow green flash | Normal: powered, no call for heat |
| Slow amber flash | Normal: the thermostat is calling and it’s heating |
| 1 red | Flame sensed with no call for heat. Shut off the gas |
| 2 red | Pressure switch closed when it should be open |
| 3 red | Pressure switch open when it should be closed: inducer, vent, hose or switch |
| 4 red | Main limit opened: the furnace overheated, filter first |
| 5 red | Rollout switch opened; it resets by hand, and it needs a tech |
| 6 red | Pressure switch opened four times in one call; locks out for an hour |
| 7 red | No flame after three tries; locks out for an hour |
| 8 red | Flame lost five times in one call; locks out for an hour |
| 9 red | Power polarity, ground or transformer wires reversed |
| 10 red | Gas valve powered with no call for heat. Shut off the gas |
| 11 red | Main limit open more than five minutes, usually the blower motor or wheel |
| 4 amber | The thermostat is calling for cooling without calling for the fan |
| Steady on, any color | The control board failed |
By symptom: what the count is telling you
It hums but never lights: 3 red flashes
What you notice: The inducer fan near the top runs, but the burners never light.
What causes it: Before the gas opens, a pressure switch has to prove the vent is clear. Three flashes means it stayed open. The manual’s list: a failing inducer, a blocked vent pipe, a broken or disconnected hose on the switch, loose wiring or the switch itself. On a high-efficiency furnace with white PVC pipes, a backed up condensate drain does the same thing.
What you can do: Clear snow, leaves or a nest from the PVC pipes where they leave the house, look for standing water in the drain hose and trap, then power cycle once.
When to call us: If 3 flashes come back, or the inducer sounds rough. The pressure switch guide goes through every cause in order; it’s written for York, and the Coleman switch works the same way.
It clicks and glows, then gives up: 7 red flashes
What you notice: The inducer runs and the igniter glows, but the burners never light or won’t stay lit. After three tries the furnace goes quiet for an hour.
What causes it: The gas valve switch left off, low gas pressure, a dirty or failed flame sensor, a cracked igniter, a bad gas valve or loose wires.
What you can do: Make sure the gas handle on the pipe beside the furnace runs in line with the pipe, then power cycle once.
When to call us: If it locks out again. The flame sensor guide covers the most common cause.
It lights, then drops out: 8 red flashes
What you notice: The burners light, then go out, over and over.
What causes it: The flame was lost five times in one call for heat, most often from a dirty flame sensor, sometimes low gas pressure or the gas valve.
What you can do: Power cycle once to clear the one-hour lockout.
When to call us: If it’s back by evening.
It blows cool air: 4 or 11 red flashes
What you notice: The burners shut off and the blower keeps running, so the vents blow cool air.
What causes it: The limit switch opened because the furnace overheated. Most often a dirty filter, then closed vents, undersized ducts or a weak blower. 11 flashes means the switch stayed open more than five minutes, which points at the blower motor or its wheel.
What you can do: Change the filter and open every supply vent and return.
When to call us: If it trips again with a fresh filter.
Codes that mean stop
1 red flash (flame with no call for heat) and 10 red flashes (gas valve powered with no call for heat) both mean gas may be flowing when it shouldn’t. Turn the furnace off at its switch and close the gas valve by turning the handle across the pipe. If you smell gas, don’t touch any switches: leave the house and call your gas company from outside. If the CO alarm is sounding, get everyone out and read what to do when the CO alarm goes off.
5 red flashes is the rollout switch beside the burners: flame came out where it shouldn’t. Leave it for a tech, because something pushed that flame out.
The modulating Coleman CP9C
The CP9C sizes its flame to the house and warns you before it quits: 4 amber flashes is poor airflow (a dirty filter or closed vents), 5 amber a blocked vent or clogged drain, rapid amber a weak flame sensor reading. It keeps heating through all three, as low as 35 percent (CP9C manual), which is your window to fix the filter or the drain.
Coleman heat pump codes (HC19B)
The Coleman HC19B heat pump has a two-digit display on the board inside the outdoor unit. There’s line voltage behind that panel, so leave it to a tech, but here’s what the numbers mean, from the manual it shares with York’s YZT and Luxaire’s HL19B (YZT manual):
Swipe to see all columns →
Swipe to see all columns →
| Code | What it means |
|---|---|
| 01 | High pressure switch open, often a dirty outdoor coil or an outdoor fan that stopped |
| 02 | High pressure trips again: 2 in 6 hours is a soft lockout, 4 soft lockouts in 12 hours a hard lockout |
| 03 | The same high pressure trips, during a defrost |
| 04 | Low pressure switch open more than 5 seconds, often low refrigerant or an iced coil |
| 05 | Cooling called with the outdoor temperature under 35°F |
| 06, 07 | Control voltage low: under 19.2 volts, then under 16 |
| 09 | Outdoor temperature sensor fault |
| 30 | System size never set at install; it shows 0t first |
Running normally, it shows a status instead: H1 or H2 for heat pump heat, A1 or A2 when backup heat is on, dd for a defrost. Iced over? Read heat pump covered in ice.
How to reset a Coleman furnace
Set the thermostat to off. Turn off the breaker or the switch for the equipment, wait about five minutes, turn it back on and set the thermostat back. Do it once. That clears the one-hour lockouts (6, 7 and 8 red flashes). If the same count comes back, a part is failing. A steady light that returns means a new control board.
Who makes Coleman now
A 2001 safety recall covered furnaces sold as York, Coleman and Luxaire, which tells you how long they’ve shared parts. Bosch has run the home heating and cooling business behind York since July 31, 2025 (Bosch announcement), using the York name under a long-term license from Johnson Controls. Bosch lists Coleman and Luxaire as its regional brands. The York furnace codes and Luxaire furnace codes read the same way.
More furnace codes
Other brands: Carrier, Goodman and American Standard, or every brand in our error codes and warning lights guide. By symptom: a furnace blinking light, a furnace that won’t turn on and a clogged or frozen drain. Our York repair page has what breaks in this family and what we charge.
Book a Coleman repair
Call (703) 997-9757 or book online. A diagnostic visit is $99, and the tech reads the code, finds the part that set it and gives you the price before any work starts. We answer day or night. Our heating check is $67 per system, through December 31: furnace, heat pump or boiler. If someone already quoted you a new system, our free second opinion looks at it first. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
What does 3 red flashes mean on a Coleman furnace?
The pressure switch didn’t close when the inducer started, so the furnace won’t light. The usual causes are a blocked vent pipe, a backed up condensate drain, a cracked hose on the switch or a failing inducer.
What does 7 red flashes mean on a Coleman furnace?
It tried to light three times without proving a flame and locked out for an hour. Make sure the gas is on and power cycle once. The flame sensor, the igniter and the gas valve are the usual causes.
Where is the code light on a Coleman furnace?
On the control board, behind the clear window low on the blower door. Leave the door on to read it, since taking it off cuts the power.
How do I reset my Coleman furnace?
Set the thermostat to off, turn off the furnace switch or breaker for about five minutes, then turn it back on. Do it once. If the code comes back, a part is failing.
Are Coleman and York furnaces the same?
They come from the same company and read the same flash codes. Bosch now runs the business, uses the York name under license and lists Coleman and Luxaire as its regional brands.
