Display shows E04 and the water heater will not fire; fan may run briefly then stop.

Safety: Turn off power before opening the cabinet. Do not operate the unit with venting disconnected.

• 1. Inspect intake and exhaust: Go outside and check the Triangle Tube vent termination. Remove any leaves, snow, ice, bird nests, or debris blocking the intake or exhaust. Ensure vent screens are clear.
• 2. Check vent length and slope: Verify that vent piping is properly supported, not sagging, and meets the maximum length and elbow count specified by Triangle Tube. Water pooling in the vent can trip the pressure switch.
• 3. Inspect pressure tubing: With power off, locate the air pressure switch and its silicone tubes to the blower or vent. Ensure tubes are not cracked, kinked, or filled with condensate. Clear any water and reattach firmly.
• 4. Test blower operation: Restore power and call for heat. Listen for the combustion blower. If it does not start or is very noisy, the blower motor may be failing. Do not bypass the pressure switch.
• 5. Check pressure switch contacts: With power off, disconnect the pressure switch wires and check continuity across the switch while gently applying suction to the tubing port (using a hand pump, not your mouth). If the switch does not change state, it may be defective.
• 6. Professional service: Replacement of the combustion blower or pressure switch should follow Triangle Tube procedures. If E04 persists after clearing vents and tubing, contact a qualified technician.