HVACopediaYork · Furnace
6 red flashes Pressure switch cycling lockout
What the control is telling you
The pressure switch opened repeatedly during a call for heat (4 times on the TM9V). The furnace locks out for 1 hour then tries again.
Applies to: York/JCI residential gas furnaces: York UTEC IFC furnaces, York White-Rodgers IFC furnaces, York TM9V
Likely causes
- Partially blocked vent or intake
- Inducer weak
- Water in the hose or drain backing up
- Marginal pressure switch
Test and repair steps
- Check vent and intake for restrictions and correct slope.
- Check the condensate trap/drain and hoses for water.
- Check the inducer for full speed.
- Test the switch and replace if it drops out at normal draft.
- To read stored codes with no thermostat call active, tap the LAST ERROR button briefly (under 5 s); up to five codes play back newest first. Two green flashes = memory empty. Hold the button 5 s or more to clear (three green flashes confirm).
Settings for these units
Clearance to combustibles · York TM9V
| Side of furnace | Upflow | Downflow | Horizontal |
|---|---|---|---|
| Top / vent / rear / side / front | ? | ? | ? |
| Combustible floor | Yes | Yes (special sub-base only) | Yes |
| Closet | Yes | Yes | Yes |
| Line contact | No | No | Yes |
Leave about 24 in. at the front and 18 in. at the side for service.
Approved for alcove and attic installs.
Filter size by return location · York TM9V
| Airflow | Cabinet | Side return filter | Bottom return filter |
|---|---|---|---|
| 1000 CFM | A | 16 x 25 in. | 14 x 25 in. |
| 1200 CFM | B | 16 x 25 in. | 16 x 25 in. |
| 1600 CFM | C | 16 x 25 in. | 20 x 25 in. |
| 2000 CFM | C | (2) 16 x 25 in. | 20 x 25 in. |
| 2000 CFM | D | (2) 16 x 25 in. | 22 x 25 in. |
Sizes assume high velocity filters (600 FPM); throwaway filters must stay at or below 300 FPM.
Filters go outside the cabinet - never inside the furnace.
Models that show this code
7 models in York UTEC IFC furnaces, York White-Rodgers IFC furnaces, York TM9V
Other codes on the same units
- 3 red flashes Pressure switch open when it should be closed
- 4 amber flashes Cooling call (Y) without fan call (G)
- 4 red flashes Main limit switch open
- 5 red flashes Rollout switch open / limit circuit open over 15 min
- 7 red flashes Ignition failure lockout (retries)
- 8 red flashes Flame lost repeatedly (recycles)
- 9 red flashes Polarity reversed or bad ground
- 10 red flashes Gas valve powered with no heat call
Save it for the next call
Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.
Source: York All JCI single-two-stage furnaces with UTEC IFC board codes ST-045-09.pdf - section Fault Code LED Flashes; York JCI single-two-stage furnaces with White-Rodgers-Emerson IFC (older installed base) codes ST-028-07.pdf - section Fault Code Sheets; York TM9V - -M9V 96% two-stage variable speed installation 1083294-UIM-A-0114.pdf - section Furnace Control Diagnostics. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.