Jacuzzi pool heater display shows F5 and the unit will not fire; blower may run briefly then stop.

Safety first: Turn off power and gas. Do not operate the heater with a suspected vent blockage; risk of carbon monoxide.

Steps to address F5:

• Inspect vent and intake: Check the flue outlet and combustion air intake (if separate) for leaves, nests, snow, or debris. Clear any obstructions. Ensure vent terminations meet Jacuzzi clearance requirements.
• Check blower operation: Restore power and call for heat. Listen for the combustion blower. If it does not start, the blower motor or its capacitor may be failed and require replacement.
• Inspect pressure switch tubing: With power off, locate the air pressure switch and its rubber or silicone tubing. Ensure tubing is not cracked, kinked, or filled with water/condensate. Replace or clear tubing as needed.
• Test the air pressure switch: Using a multimeter, verify that the switch closes when the blower runs. If it remains open despite proper airflow, replace the switch with a Jacuzzi-compatible air pressure switch.

If F5 persists after clearing vents and verifying the switch and blower, contact a qualified technician to evaluate the combustion system and venting.