Carrier furnace Status code 13: Limit circuit lockout

Code 13 means a limit or flame rollout switch stayed open for more than three minutes, so the control locked out. It is the escalated form of code 33 and clears itself after three hours.

Applies to: Carrier 58MCB four-way multipoise condensing gas furnaces and related models using the same integrated furnace control. Bryant and Payne furnaces of the same generation use the same control and code set.

What it means

The limit circuit includes the high limit switch and the flame rollout switch, and the control watches it continuously. A brief opening produces code 33 while the blower cools things down. If the circuit stays open longer than three minutes, the control escalates to a lockout and displays code 13. It resets automatically after three hours, which produces the characteristic pattern of a furnace that works for one cycle every few hours and then stops again. That is not recovery — it is the lockout timer expiring and the same fault recurring. The underlying cause is whatever opened the limit circuit, which Carrier's own documentation directs you to code 33 to investigate.

Most common causes

• Sustained overheating from restricted airflow — a dirty filter is the most common single cause.
• A flame rollout switch open, which is a serious condition requiring manual reset.
• A blower that is not running, or running too slowly for the furnace's output.
• A restricted or blocked vent.
• Blocked filters or a restrictive duct system.
• A defective blower motor or capacitor.
• A defective limit switch or a loose connection in the limit circuit.

How to diagnose it

1. Read code 33's causes as well, since Carrier's documentation explicitly refers this code there.
2. Check the air filter first. It is the most common cause and the easiest to check.
3. Note the three-hour pattern. A furnace that runs once every few hours and stops is displaying exactly this behaviour.
4. Check whether the blower runs when the furnace fires. If it does not, overheating is guaranteed.
5. Note whether a flame rollout switch is involved, since those require manual reset and indicate a much more serious condition than a dirty filter.

How to fix it

1. Replace the air filter and open closed registers. This resolves a large share of limit circuit faults.
2. If the cause is a flame rollout switch, stop and call a technician. Do not press the reset button.
3. Blower motor faults, duct problems, vent restrictions, and limit switch replacement are technician work.
4. Do not keep letting the furnace lock out and restart on the three-hour timer. Each cycle is another overheating event, and repeated overheating is what cracks heat exchangers.

Notes

The automatic three-hour reset makes this fault easy to live with and expensive to ignore. A furnace that heats intermittently through a cold spell may look like it is coping while it is repeatedly overheating its heat exchanger.

Related

• Status code 33 — Limit circuit fault — a limit or flame rollout switch is open
• Status code 14 — Ignition lockout

All codes for this manufacturer

Carrier, Bryant and Payne furnace status codes — every code, with what differs between models.

Do it yourself or call a technician?

The fifteen-dollar filter is the only part a homeowner should be buying against this code. Replace it, open the registers, confirm the return grille is clear — those are documented causes and cost nothing to rule out. One observation is also safely yours: whether the furnace comes back by itself (a limit switch, released by the three-hour timer) or stays down until a button is pressed (a rollout switch — much more serious). Report that distinction; do not act on it. Past that line everything is professional work: capacitor and blower faults are live-cabinet electrical repairs, a limit switch that keeps tripping is doing its job against a real overheating problem that has to be found, and a tripped rollout switch means flame left the burner compartment — call-now territory, and never a switch to reset yourself. Above all, do not ride the three-hour timer through a cold week: each automatic restart is another overheating event on the same heat exchanger.

The same fault on other brands

Carrier is unusual in splitting this fault across two codes — 33 while the circuit is open, escalating to 13 once it has stayed open past three minutes. Most families flash one open-limit code for the whole event: Goodman's 4 flashes, Lennox alert 250, Trane's 4 flashes, Rheem's 3 blinks. The limit switch codes hub collects 17 of them across 11 control families, and its central point applies doubly to the lockout version: the cause is almost never the switch itself. If the rollout half is what tripped, the rollout switch codes hub maps those equivalents.

What the fix costs

If the fix is the filter, it costs the price of the filter. The paid outcomes, priced from the repair cost guide: a limit switch runs $150–350 — with the guide's caution that the visit should find why it tripped, not just change the part — and the blower-side causes Carrier lists sit at $150–350 for a run capacitor or $400–700 installed for this chassis's PSC blower motor. The number that makes this code worth respecting is the one you are trying to avoid: repeated lockout-and-restart cycles are repeated overheating, overheating is what cracks heat exchangers, and at $1,000–2,500+ the guide calls the heat exchanger the usual replace-the-furnace moment.

What this looks like

From the outside, this usually shows up as the furnace heats then trips out on high limit — that walkthrough covers what to check in order, and when it stops being a homeowner job.

This can also show up as a burning or gas smell from the unit — that page sorts the normal smell from the ones that mean shut it down.

Sources

• Carrier 58MCB Service Manual, 327884-101 Rev. B — status codes