2+7
Low pressure switch opened during ignition trial or heating demand
This code typically points to
- Marginal venting
- Wind effect
- Intermittent inducer performance
- Condensate restriction
Next checks to confirm
- Verify switch remains closed through ignition and run
- Check vent, intake, and condensate path
- Measure running pressure in inches w.c.
Escalation
Recycle / retry behavior; may lead to watchguard
Reset behavior
Clears when pressure switch remains proven during a successful heat call.
Urgent
Fix now