Goodman Furnace: Auxiliary limit switch open (blower compartment)

Auxiliary limit switch open (blower compartment) on a Goodman furnace: This one means the auxiliary limit in the blower compartment is open, and the furnace will not run until it closes. It is a safety, so it is telling you something got too hot or lost power at the wrong moment. Think about airflow first, since a clogged filter or a slow blower is the most common reason, and then the wiring. If the 115 V supply was shut off in the middle of a heat cycle, the limit can trip from residual heat, and that is a one-off rather than a fault.

Homeowner with a furnace problem? Call (647) 657-2977 or book a service call — licensed technicians across Vaughan and the GTA.

Applies to: 34.5 in chassis gas furnaces

Common causes of auxiliary limit switch open (blower compartment)

• 115 V power supply shut off during heat cycle
• Not enough conditioned air over the heat exchanger from blocked filters, restrictive ductwork, improper circulator blower speed or failed motor
• Loose or improperly connected wiring in the high limit circuit
• Closed dampers or registers cutting airflow

How to fix auxiliary limit switch open (blower compartment): step by step

1. Turn power off before repair and let the cabinet cool
2. Check filters and ductwork for blockage. Clean filters or remove obstructions
3. Check circulator blower speed and performance. Replace motor if needed
4. Tighten or correct the wiring connection at the limit
5. Check continuity across the limit with the wires off, only when cold
6. Restore power and run a full cycle, watching that the blower and burners behave normally
7. If it trips again, find the cause before resetting, and call a licensed tech if you cannot

If the unit shows an error code, look it up: Goodman Furnace codes