Furnace cycles off when another large exhaust fan (kitchen, bath, dryer) runs.

Safety: Inadequate combustion air can cause backdrafting and CO issues.

• Check intake (if applicable): For sealed combustion York furnaces with PVC intake, ensure the intake pipe is clear outside.
• Reduce competing exhaust: Avoid running large exhaust fans continuously while the furnace operates.
• Provide combustion air: Open a window slightly near the furnace room as a temporary test. If operation stabilizes, permanent combustion air openings or ducts are needed.
• Professional design: Have an HVAC professional size and install proper combustion air per code.