Boiler display shows E4 and burner will not start, fan may run briefly on condensing models

Safety first: Turn off power and gas before working on venting. Exhaust gases are hazardous.

• Inspect venting: Check the flue pipe from the boiler to the chimney or termination. Look for obstructions, sagging sections, or disconnected joints. On PVC vented Pennco boilers, ensure terminations are clear of snow, leaves, or nests.
• Check condensate drain: On condensing models, locate the condensate trap and drain tubing. Clear any sludge or debris and ensure the drain line slopes properly and is not frozen.
• Test flue pressure switch tubing: Inspect the silicone tubing from the inducer fan to the flue pressure switch. Make sure it is not cracked, kinked, or filled with water.
• Reset and test: Restore power and attempt a reset. Listen for the inducer fan starting. If the fan does not run or stops quickly, the inducer motor or control board may be faulty.
• If E4 persists: The flue pressure switch or inducer assembly may need replacement. This should be handled by a qualified technician who can verify proper draft and combustion.