York, Coleman, and Luxaire furnaces are built on the same manufacturing platform: historically under Johnson Controls, and under Bosch since Bosch acquired Johnson Controls’ residential HVAC business in a deal that closed July 31, 2025. The control boards, parts, and diagnostic logic are shared across all three nameplates. But flash-code meanings are tied to the control board installed in your specific furnace, not to the brand name on the door. A furnace built in 2010 and one built in 2022 can use completely different code maps even under the same brand. Count your blinks, then match them against your furnace’s own door sticker or manual before acting on any chart, including this one.
Are York, Coleman, and Luxaire really the same furnace?
Yes, at the manufacturing level. All three are nameplates built on shared platforms under the same corporate parent (Johnson Controls historically, Bosch now), and installation manuals published during the JCI era cover multiple brands under one document for a given model line. Parts (igniters, flame sensors, pressure switches, gas valves) are cross-catalogued and interchangeable across the three brands for a matching model.
What is not shared automatically: the flash-code table. Two furnaces from two different brands but the same control-board generation will match. Two furnaces from the same brand but different board generations often won’t. This guide documents the code chart for the TM9V*C-series two-stage variable-speed board (the control used in a large share of current 96% AFUE York, Coleman, and Luxaire condensing furnaces), verified against the manufacturer’s own installation manual.
How to read the LED
- Open the furnace’s lower door panel. The LED is on the integrated control board.
- Slow green flash (2 seconds on, 2 seconds off): normal operation, no thermostat call.
- Slow amber flash: normal operation, actively running a heat call.
- Counted red flashes: on 1/3 second, off 1/3 second, repeated the number of times equal to the code, then a 2-second pause before repeating. Count a full cycle twice to confirm.
- LED steady off: no power to the board, or a blown fuse on the board.
- Steady on, any color: control board failure. Cycle power; if the LED stays steady on, the board needs replacing.
Most common fault by far: Code 3 (pressure switch didn’t close), usually from a blocked condensate drain on a condensing furnace. Check that first.
York/Coleman/Luxaire TM9V-series flash codes: verified chart
| Flashes | Fault | What it means | DIY or call? |
|---|---|---|---|
| Slow green | Normal, no call | Standby | N/A |
| Slow amber | Normal, heat call | Running normally | N/A |
| Steady off | No power / blown fuse | Check breaker, door switch, board fuse | DIY check |
| Steady on (any color) | Control failure | Cycle power; replace board if it recurs | Call a pro |
| Continuous amber | Flame sense current below 1.5 microamps | Dirty flame sensor or low gas flow | DIY start |
| 1 red | Flame sensed with no call for heat | Leaking or slow-closing gas valve | Call a pro |
| 2 red | Pressure switch stuck closed | Faulty switch, water in the hose, or miswiring | DIY check |
| 3 red | Pressure switch failed to close | Blocked condensate drain, blocked vent, faulty inducer | DIY check |
| 4 red | Main limit switch open | Dirty filter, restricted airflow, blower issue | DIY first |
| 5 red | Limit circuit open 15+ minutes | Manual-reset rollout switch trip (hard lockout) | Call a pro |
| 6 red | Pressure switch opened 4x during a call for heat | Intermittent inducer or pressure-switch fault | Call a pro |
| 7 red | Flame not established after 3 ignition trials | Gas valve, igniter, flame sensor, or low gas pressure | DIY start, call if unresolved |
| 8 red | Flame lost 5 times (4 recycles) during the heat cycle | Low gas pressure, dirty/faulty flame sensor, faulty gas valve | DIY start, call if unresolved |
| 9 red | Reversed line-voltage polarity or grounding fault | Furnace wiring, disconnect, or panel connection | Call an electrician |
| 10 red | Gas valve energized with no call for heat | Gas valve or gas valve wiring fault | Call a pro |
| 11 red | Limit circuit open 5–15 minutes | Likely failed blower motor or blower wheel | Call a pro |
| 12 red | Loose or missing model ID plug | Reseat or replace the ID plug | DIY check |
| 13 red | High-fire pressure switch open when it should be closed | Partially blocked vent, loose wire, or faulty switch | DIY check, call if unresolved |
| 4 amber | Thermostat sending Y (cool) without G (fan) | Wiring problem at the thermostat, not a failure | DIY check |
Confirm against the sticker on your own door panel. This chart documents the TM9V*C two-stage variable-speed board. If your furnace uses a different control board, including an older York, Coleman, or Luxaire from a prior generation, the numbers can mean something different. Match the model number on your rating plate to your furnace’s own manual before acting on any code.
Code-by-code: what to check first
2 red flashes: Pressure switch stuck closed
The board found the pressure switch closed before the inducer started, when it should read open. Check for water pooled in the rubber hose between the switch and the inducer housing, and drain it. Test the switch with a multimeter: it should show no continuity at rest.
3 red flashes: Pressure switch failed to close
The inducer started but draft pressure never registered. On a condensing furnace (90%+ AFUE), a blocked condensate drain trap is the leading cause. Clear it with a wet-dry vac at the drain outlet or by flushing with water. On an 80% AFUE unit with no condensate drain, check the metal flue pipe for a blockage (bird nests, rust, ice in extreme cold).
4 red flashes: Main limit switch open
The furnace overheated and the limit switch tripped to protect the heat exchanger. Check the filter first, every time. A clogged filter is the leading cause. Replace it, cycle power off for 30 seconds, and restore. If Code 4 returns with a clean filter, check for closed supply registers, a blocked return grille, or a blower wheel caked in dust.
5 red flashes: Manual-reset rollout switch (hard lockout)
The limit circuit stayed open for more than 15 minutes, which the control reads as a rollout switch trip: flames burning outside the burner box. Causes include a blocked flue, abnormally high gas pressure, or a cracked heat exchanger.
Safety box: stop using the furnace and close the manual gas shutoff valve. This is a hard lockout. Power must be cycled to reset it, and the control will not auto-restart. A cracked heat exchanger from a rollout event can put carbon monoxide into the living space. Call a licensed HVAC technician before restarting; do not reset and walk away.
7 red flashes: Flame not established after 3 ignition trials
The furnace tried to light three times and failed. Check that the manual gas shutoff is fully open, then work through gas pressure, a cracked or dirty hot-surface igniter, and a dirty flame sensor (clean the metal rod with 0000 steel wool). See Furnace Hot-Surface Igniter: Symptoms and Replacement and Furnace Flame Sensor: Symptoms and Cleaning. The furnace locks out for one hour and retries on its own.
9 red flashes: Reversed polarity or grounding fault
The 115V supply has reversed hot/neutral, or the ground connection is missing. The furnace will not start ignition until this is fixed. Call an electrician or HVAC tech to check the furnace wiring, disconnect, and panel connection. Don’t attempt line-voltage wiring yourself unless you’re qualified.
When to call a licensed HVAC technician
- Code 5 (rollout, hard lockout) or 9 (polarity/grounding): don’t reset and rerun. Get it inspected first.
- Code 6, 8, or 10 if the fault keeps returning after your own checks.
- Any gas-valve or ignition fault (1, 7, 10) that isn’t resolved by a first pass at the filter, igniter, and flame sensor.
- Steady-on LED after a power cycle: the control board itself has failed.
FAQ
Are York, Coleman, and Luxaire furnaces really the same? The brands share a manufacturing platform, control boards, and parts, historically under Johnson Controls and now under Bosch. But the flash-code meanings depend on which control board generation is in your specific furnace, not the brand name. Always confirm against your unit’s own door sticker or manual.
How do I reset my York or Coleman furnace after a lockout? Turn the power switch off for 30 seconds, then restore. This clears a soft lockout. A hard lockout (Code 5, 9, 11) also requires the power cycle, but don’t do it repeatedly without fixing the underlying cause. Cycling power on a live gas-valve or rollout fault is how a real problem gets ignored.
Code 3 shows up every cold morning. What’s happening? On a condensing furnace, the condensate drain trap is a common freeze point if it runs through an unheated basement or garage wall. Insulate the trap, or add a small amount of RV antifreeze to the trap to prevent overnight freezing.
My furnace shows Code 4 and the blower sounds slow. Is that related? Yes. A slow blower reduces airflow across the heat exchanger, which is exactly what trips the limit switch. Check the blower capacitor first (a $10–25 part and the most common cause of a weak blower) before assuming the motor itself has failed.
Related guides
- York HVAC: Brand Overview, Reliability, and Repair Help: product lines, Affinity vs. LX tiers, the Coleman/Luxaire relationship, serial number age lookup
- Furnace Not Heating: Diagnostic Order: use this if no fault code is showing and the furnace simply isn’t heating
- Furnace Flame Sensor: Symptoms and Cleaning: Codes 1, 7, and 8 (flame-related faults) lead here
- Furnace Hot-Surface Igniter: Symptoms and Replacement: Code 7 (no ignition) with no igniter glow leads here
Last reviewed August 2026. Flash-code meanings are specific to your control board generation. Verify against your furnace’s own door sticker or manual before acting.
