What This Error Means

The furnace control detects an open inducer-limit switch or condensate pressure switch. Normal heating is interrupted because the furnace cannot confirm an acceptable inducer or condensate condition.

Symptoms You May Notice

No heat; burners shut down; inducer may run; water may be visible near the furnace or drain; the fault may occur during longer heating cycles; furnace may restart after cooling or draining and then fault again.

Common Causes

Blocked condensate trap or drain; frozen or improperly sloped drain line; water backed up in the furnace; open condensate pressure switch; overheated inducer; restricted venting; failing inducer motor; loose wiring or connector; defective safety switch.

Safe Troubleshooting Steps

1. Turn off furnace power. 2. Check for visible water leakage or a backed-up condensate drain. 3. Inspect the external drain tubing for kinks, freezing or blockage without disturbing sealed components. 4. Check intake and exhaust terminations for visible obstruction. 5. Allow an overheated inducer to cool, but do not repeatedly reset the furnace. 6. A qualified technician should inspect and clean the condensate system, verify inducer current and temperature, test switch continuity and confirm venting and drain installation.

Parts Commonly Involved

Condensate trap and drain; condensate pressure switch; inducer motor and limit; intake and exhaust venting; wiring; integrated furnace control.

When to Call a Technician

Recommended. Call promptly if water is leaking, the drain repeatedly backs up or the fault returns after an obvious external blockage is cleared.

Safety Notice

Turn off power before inspecting condensate components. Do not bypass inducer or condensate safety switches, and do not operate the furnace if water is entering electrical areas.

Manufacturer Documentation