HeatingCodesCarrier furnace status code 13: limit circuit lockout
What code 13 means
Carrier's table defines code 13 as Limit circuit lockout: "Lockout occurs if a limit or flame rollout switch is open longer than 3 minutes. Control will auto reset after three hours. Refer to #33." So the furnace first reports code 33, and if the open switch does not close within three minutes the control escalates to code 13.
The lockout codes side by side
It is easy to mix up the lockouts. This table is taken directly from the Carrier SP05-59 status code list:
| Code | What it is | Reset behavior (per Carrier) |
|---|---|---|
| 13 | Limit circuit lockout: limit or rollout switch open longer than 3 minutes | Control auto-resets after three hours. See code 33. |
| 14 | Ignition lockout: ignition not proved | Control auto-resets after three hours. See code 34. |
| 21 | Gas heating lockout | Control will not auto-reset. Check for a mis-wired gas valve or defective control (valve relay). |
| 45 | Control circuitry lockout | Auto-resets after a one-hour lockout. Reset power to clear it; replace the control if the code repeats. |
What the three-hour auto-reset means for you
If your furnace has locked out on code 13, it may start working again by itself a few hours later. That does not mean the problem went away. The switch may simply have cooled and closed. If the furnace heats for a while and then locks out again, the underlying cause (airflow, venting, a switch or the blower) is still there.
You can also read earlier codes from the control. Carrier says the control stores status codes (the stored codes are erased automatically after 72 hours) so a technician can see what happened before the lockout.
What to check, and what to leave alone
Start with the same low-risk checks as code 33: a clean filter, open supply and return vents, and clear outdoor vent terminations. Carrier's own list for the limit circuit also includes a loose blower wheel, a defective blower motor or capacitor, a defective switch or connections, vent sizing, a restricted vent and inadequate combustion air for a rollout switch. Those need a technician with the furnace manual.
Frequently asked questions
How long does Carrier code 13 last?
Carrier says the control will auto reset after three hours. If the cause is still present, the furnace can lock out again.
Can I clear code 13 by turning the power off?
The Carrier table says code 13 auto-resets after three hours. The service procedures also describe interrupting power as a way to clear some codes, but repeated resets can hide a safety problem, so call for service if it returns.
Is code 13 caused by a dirty filter?
A dirty filter or restricted duct system is the first item on Carrier's check list for the limit circuit, so it is the best first thing to check. It is not the only possible cause.
Sources
- SP05-59 Service and Maintenance Procedures: Deluxe 4-Way Multipoise 2-Stage Direct-Vent Condensing Gas Furnace (Carrier (shareddocs.com)) Covers: Carrier 2-stage condensing gas furnaces with the status-code LED control described in the document. Other Carrier, Bryant and Payne boards can use different codes; check the service label on your furnace.
Safety note: this page is general information drawn from the sources above. Gas, combustion and line-voltage repairs belong to a licensed professional. Your own equipment's label and manual take priority over anything here. Read the full disclaimer.