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Carrier furnace status code · Sources read 2026-11-01

Carrier Furnace Code 42: Inducer Motor Fault

If you smell gas or a CO alarm sounds, leave the home and call the gas utility or 911 from outside.

Code 42 is an inducer motor fault. Carrier's 58MVP-family and 59MN7A guides say the inducer did not start within 20 seconds of a call for heat, ran outside its valid speed range, or lost its RPM signal for 5 seconds. The checks are vent sizing, a restricted vent or air supply, a failed inducer motor and its wiring.

Talk to a contractor about your Carrier furnace code 42

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HVAC Responder Editorial Team · Reviewed 2026-11-01 · Facts quoted from manufacturer documentation

HVAC Responder is an independent referral service and is not affiliated with or authorized by Carrier.

How code 42 looks on the furnace light

On these Carrier furnaces the status light shows code 42 as 4 short flashes, then 2 long flashes . Carrier’s 58MVP (Series 170 & 180), 58MVB, 58UVB troubleshooting guide (58-06T) explains 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 42 means, by furnace series

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

Carrier’s 58MVP (Series 170 & 180), 58MVB, 58UVB troubleshooting guide (58-06T) lists code 42 as:

42 INDUCER MOTOR FAULT – Indicates the inducer has not started within 20 seconds after a call for heat, the inducer motor RPM is outside its valid range of operation, or the inducer RPM signal was lost for 5 seconds during operation.

Checks listed in the same guide:

  • Listed check: “Proper vent sizing.”
  • Listed check: “Restricted combustion air supply.”

Discuss your Carrier furnace code 42 with a contractor

Call (877) 565-3062

One call reaches a contractor registered for your ZIP; ask the fee and the arrival window.

  • Listed check: “Failed inducer motor.”
  • Listed check: “Improper motor wiring.”

59MN7A (Series 100)

Carrier’s 59MN7A (Series 100) troubleshooting guide (59MN7A-01T) lists code 42 as:

42 INDUCER MOTOR FAULT – Indicates the inducer has not started within 20 seconds after a call for heat, the inducer motor RPM is outside its valid range of operation, or the inducer RPM signal was lost for 5 seconds during operation.

Checks listed in the same guide:

  • Listed check: “Proper vent sizing.”
  • Listed check: “Restricted vent.”
  • Listed check: “Failed inducer motor.”
  • Listed check: “Improper motor wiring.”
  • Listed check: “Blockage in the tubing to the pressure switch assembly or blockage in the pressure tap at the collector box.”

Discuss your Carrier furnace code 42 with a contractor

Call (877) 565-3062

One call reaches a contractor registered for your ZIP; ask the fee and the arrival window.

Does code 42 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 58MVP (Series 170 & 180), 58MVB, 58UVB troubleshooting guide (58-06T) starts with: “DO NOT REMOVE BLOWER ACCESS PANEL! Record status of AMBER LED.” Turning off power can also clear the code history.
  • Everything else on these lists (gas valve, pressure switches, wiring, venting, the control board) is technician work.

Related codes

All Carrier furnace codes

Furnace guides for the wider symptom

Sources

Related equipment, symptoms and component guides

Use each guide with its named equipment and source. A symptom or code alone does not select a replacement part.

What happens when you call about your Carrier furnace code 42

  • Your call routes to an independent local contractor registered for your ZIP code.
  • Ask the fee and the arrival window.
  • The decision to hire stays with you.
Call (877) 565-3062

One call reaches a contractor registered for your ZIP; ask the fee and the arrival window.

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