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Carrier furnace status code · Sources read 2026-10-31

Carrier Furnace Code 31: High Pressure Switch Did Not Close

By the HVAC Responder Editorial Team

Quoted from Carrier troubleshooting guides, read 2026-10-31. Not reviewed by a licensed HVAC professional.

Code 31 means the high-heat pressure switch (medium or high on modulating 59MN7A furnaces) did not close on a call for that stage of heat, or opened during it. Carrier's guides say a control relay may be defective or the gas valve mis-wired, and refer to code 32 for the remaining checks.

How code 31 looks on the furnace light

On these Carrier furnaces the status light shows code 31 as 3 short flashes, then 1 long flash . The guides explain the pattern:

EACH OF THE FOLLOWING STATUS CODES IS A TWO DIGIT NUMBER WITH THE FIRST DIGIT DETERMINED BY THE NUMBER OF SHORT FLASHES AND THE SECOND DIGIT BY THE NUMBER OF LONG FLASHES.

Codes differ between furnace generations, so match the series on your furnace’s rating plate to the guide below.

What Carrier’s guides say code 31 means, by furnace series

58CVA / 58CVX

Carrier form TG-GFC80-02, mid-efficiency variable-speed two-stage furnaces

31 HIGH-HEAT PRESSURE SWITCH OR RELAY DID NOT CLOSE OR REOPENED – Control relay may be defective or gas valve is mis-wired. Refer to status code #32.

58MVP (Series 170 & 180), 58MVB, 58UVB

Carrier form 58-06T, variable-speed two-stage condensing furnaces

31 HIGH-HEAT PRESSURE SWITCH OR RELAY DID NOT CLOSE OR REOPENED – Indicates the high-heat pressure switch input failed to close on a call for high-heat, or opened during high-heat. Control relay may be defective or gas valve is mis-wired. Refer to status code #32.

59MN7A (Series 100)

Carrier form 59MN7A-01T, variable-speed modulating condensing furnaces

31 MEDIUM PRESSURE SWITCH, HIGH PRESSURE SWITCH, OR PSR RELAY DID NOT CLOSE OR REOPENED – Indicates the medium or high pressure switch input failed to close on a call for intermediate- or maximum-heat, or opened during a heat cycle. PSR relay may be defective. Refer to status code #32.

Does code 31 reset on its own?

The guides do not describe an automatic reset for this code.

What to do before you call

  • Write the code down before you touch anything. Carrier’s guides start with: “DO NOT REMOVE BLOWER ACCESS PANEL! Record status of AMBER LED.” Turning off power can also clear the code history.
  • If you smell gas, leave first, then call the utility.
  • Everything else on these lists (gas valve, pressure switches, wiring, venting, the control board) is technician work.

Get the furnace looked at

One call routes you to an independent local heating contractor. Tell them the code and the furnace series, and ask the diagnostic fee up front.

Call (877) 565-3062

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Related codes

All Carrier furnace codes

Furnace guides for the wider symptom

Sources

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