Carrier · Status code
Carrier 59TP7A status code 33: limit circuit, high-heat or ignition lockout
Major code 33 has three meanings on the 59TP7A label. Minor 33.1: a switch in the main limit circuit has opened. Minor 33.2: the control locked the furnace to low heat for the current cycle because the high-heat conditions were not met. Minor 33.3: ignition failed during four consecutive trials.
Smell gas?
- Do not operate light switches, appliances or phones inside.
- Leave the building and leave the door open behind you.
- From outside, call the FortisBC emergency line at 1-800-663-9911 or 911.
- Only after that, call BC Wide about the furnace.
A furnace that will not run is a breakdown, not a gas emergency. Gas smell, a CO alarm, soot or scorching are.
On the control
- Code
- 33
- Minor
- 33.1 · 33.2 · 33.3
- Door LED
- 3 short flashes then 3 long
- Controller
- 59TP7A integrated furnace control with 3-digit LCD display and door LED
- Applies to
- Carrier Performance 97 (59TP7A)
- Manual
- 59TP7A-01SI
What each minor code says, verbatim
| Display | Manufacturer wording |
|---|---|
| 33.1 | A switch has opened in the Main Limit circuit |
| 33.2 | Lockout - High Heat Only for current cycle |
| 33.3 | Ignition fault - during four consecutive ignition trials |
A code is a condition, not a diagnosis
Each sub-code has its own cause tree. 33.1 mirrors code 13.1 but is reported as a distinct minor: airflow restriction, blower failure, or a combustion problem that opened a limit or rollout switch. 33.2 is the two-stage control protecting high fire when the high-heat pressure switch or another high-fire condition fails. 33.3 is the same family of causes as code 13.2's ignition trials. On-site testing distinguishes them; the code is a condition, not a part.
Which furnaces this applies to
Documented for Carrier 59TP7A furnaces (all nine sizes) in installation instructions 59TP7A-01SI REV A, edition 06/23. The main limit circuit includes the burner-area manual-reset limit switch that opens on flame rollout; Carrier states it must never be jumpered and must be reset only after the cause is corrected.
Scope: Carrier 59TP7A Performance 97 furnaces with the on-board 3-digit display control. Not sure which control you have? Send us the full model number from the rating plate.
Safe things to look at first
- Read the full code on the control display through the door, including any minor digit (for example 33.2), and write it down.
- Look, without touching, for obvious conditions you can report: snow or ice at the vent terminations, water on the floor, a loaded filter, a condensate pump that is full or off.
- Note whether the furnace still heats at all, and how long it runs before the code returns.
- For 33.1: report any warm smell, whether the blower runs, and the filter condition.
- For 33.2: note whether the furnace still heats on low fire and whether the code clears next cycle.
- For 33.3: confirm the gas shut-off is on and report whether the inducer runs before the trials start.
- If you smell gas, leave the building and call FortisBC at 1-800-663-9911 or 911 first.
Do not
- Do not bypass or jumper the door switch, limit switches, rollout switches or pressure switches.
- Do not open the burner compartment, disconnect tubing, or adjust the gas valve or gas pressure.
- Do not keep cycling power to force the furnace to relight; repeated resets hide the fault and can allow unburned gas to build up after ignition failures. If the code returns, stop and call.
Homeowner-safe checks (look and read only)
- Check the filter and that supply registers are open
- Note whether the blower runs during the cycle
- If you smell gas or a CO alarm sounds, leave and call FortisBC at 1-800-663-9911 or 911
When to call a technician
- If the code returns after the furnace cools
- Immediately, if you smell gas or a CO alarm sounds
What a technician does
- A technician checks every switch in the main limit circuit, measures temperature rise and static pressure, and confirms the cause of any rollout before resetting a manual-reset switch.
- For 33.2 the high-heat pressure switch circuit, inducer performance and venting are tested with a manometer.
- For 33.3 gas supply, ignitor, flame sensing and combustion-air conditions are tested before the fault history is cleared.
Same code, other equipment
- Carrier single-stage sibling controls (59SC6A): On the single-stage Comfort 96, code 33 has only the limit-circuit meaning (33.1) and its ignition codes sit under 34. Read the label on your own furnace. source
Related components and symptoms
Questions people ask
What is the "Main Limit circuit" on my furnace?
It is the series of safety switches that stop the burner if the furnace overheats, including the limit switch near the heat exchanger and the manual-reset switch in the burner area that responds to flame rollout.
Code 33.2 says the furnace runs low heat only. Can I keep using it?
The control has already decided to protect the furnace by staying in low heat for that cycle. Use it temporarily if you must, but have the cause found; a high-heat problem left alone can become a no-heat call.
Seeing code 33 on your Carrier?
Tell us the full code, the model number and whether the furnace still heats on low. BC Wide prioritizes no-heat calls across Greater Vancouver.