HVACopediaLennox · Furnace
10 flashes Watchguard - pressure switch opened 5 times in one heat demand
What the control is telling you
Pressure switch opened 5 times in one heat call, so the control is in a 1 hour lockout.
Applies to: EL195UHNE furnaces with ignition control 103217-03 or 107163-01 (red LED)
Likely causes
- Intermittent vent restriction (wind, ice)
- Partially plugged condensate drain
- Loose/leaking switch hoses
- Marginal inducer
Test and repair steps
- Check vent terminations for icing or wind effects and that intake/exhaust separation and clearances are correct.
- Clean and prime the condensate trap; check the drain line slope (1/4 in. per ft).
- Inspect switch hoses and screens.
- Measure switch differential during a long run (set point 0.50 in. w.c.).
- Reset by cycling power or thermostat after repair.
Settings for these units
- Filter sizes (filter rack kits) · Lennox EL195UHNE
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Source: Lennox EL195UHNE Unit Information Corp 1801-L1 (rev 04/2024), Table 4 (103217-03) / Table 5 (107163-01) diagnostic codes, p.8-10. Summarized in our own words; check the original manual for your model.
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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.