Error code reference
Trane Furnace Error Code ERR 34
Line polarity fault
Line polarity fault – voltage reverse polarity detected.
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Get the full diagnostic procedure for ERR 34.
- ✓Step-by-step tests with expected resistance, voltage, and continuity values
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ERR 34 on my Trane Furnace
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Line polarity fault – voltage reverse polarity
From Service Manual 660286, p.18:
1.Access service mode to confirm the active fault code and read stored error history.
2.Measure line voltage at the power cord terminal block. Expected: 120 VAC (L1 to neutral) or 208 to 240 VAC between L1 and L2 under load.
3.Inspect the cord strain relief and terminal block screws for signs of arcing or heat discoloration. Loose connections here mimic an intermittent power failure to the control board.
Part W10911048
Power cord assembly
Related Trane furnace codes
All Trane furnace codes →- 1Flame sensed when no flame should be present.
- 1 Flash (Red)Normal LitePort data transmission
- 1 GREENStandby mode or call for cooling.
- 1 GREEN / 1 AMBER1st stage call for heat.
- 1 REDFlame sensed when no flame should be present.
- 10Gas valve energized without call for heat.
- 10 FlashCommunication fault
- 10 REDGas valve energized without call for heat.
View all 78 Trane furnace codes
- 11Primary limit has been open for more than 5 minutes, check…
- 12Ignitor relay failure internal in board
- 12 REDIgnitor relay failure internal in board
- 2Pressure switch is stuck closed.
- 2 FlashFlame lost or ignition failure
- 2 GREEN / 1 AMBER2nd stage call for heat.
- 2 REDPressure switch stuck closed.
- 31st stage pressure switch is stuck open (not closing).
- 3 Double2nd stage pressure switch open
- 3 DOUBLE RED2nd stage pressure switch open; system reverts back to 1st…
- 3 FlashPressure switch or inducer error
- 3 GREEN / 1 AMBERW2 call present without W1.
- 3 RED1st stage pressure switch is open or not closing.
- 4Open primary limit, flame roll out or reverse flow switch.
- 4 FlashHigh temperature limit fault
- 4 GREEN / 1 AMBERY call present without G.
- 4 REDOpen thermal limit or open rollout.
- 5Open roll out switch or open low voltage fuse.
- 5 FlashFlame detect fault
- 5 REDOpen low voltage fuse.
- 61st stage pressure switch has opened 5 times within one…
- 6 FlashLine polarity fault (voltage reverse polarity), ground…
- 6 RED1st stage pressure switch opened 5 times within one cycle
- 7System lockout Retry
- 7 FlashExternal gas valve circuit error
- 7 REDSystem lockout Retry.
- 8System lockout Recycle
- 8 FlashLow flame sense signal
- 8 REDSystem lockout Recycle.
- 9Reverse polarity or poor grounding.
- 9 FlashOpen inducer limit error
- 9 REDReverse polarity or poor grounding.
- CFMB Blinking Red LEDFasco Motor Control Board (CFMB) has shut down due to…
- ERR 10Ignition means fault
- ERR 101Y1 relay failure
- ERR 114Bad or missing personality module
- ERR 119Temperature sensor failure
- ERR 139Communication failure
- ERR 18Internal control failure.
- ERR 22Soft lockout due to flame lost or ignition retries (10…
- ERR 26High temp limit fault
- ERR 87Flame detect fault
- ERR 91Communication fault
- ERR 93Gas valve fault
- Fast FlashPersonality Module error
- Green Continuous / Red FlashingGas valve miswired or flame signal present at a call for…
- Green Fast FlashNormal operation, call for heat present.
- Green OFF / Red ContinuousInternal fault detected on Texas Instruments ignition…
- Green OFF / Red FlashingIgnition control module locked out on failure to establish…
- Green OFF / Red Flashing (during ignition try)No flame signal on try for ignition or flame signal lost…
- Green Slow FlashNormal operation, no call for heat.
- Green/Red LEDs on continuouslyFuse open or internal control failure.
- None (AC VOLTS HI)AC line voltage too high.
- None (AC VOLTS LOW)AC line voltage too low.
- None (CAP MISMATCH)Compressor size does not match capacity in Personality…
- None (CHECK FUSE)24V control fuse is open.
- None (ID MTR ERR)Blower HP/OEM does not match Personality Module data.
- None (TS 1 OPEN)Temperature sensor 1 is open.
- None (TS 1 SHORT)Temperature sensor 1 is shorted.
- None (TS 2 OPEN)Temperature sensor 2 is open.
- None (TS 2 SHORT)Temperature sensor 2 is shorted.
- None (TWIN ERROR)Twinning not allowed with variable speed
- None (Y1 OFF ERR)Y1 relay failure
- None (Y1 ON ERR)Y1 output is ON when it should be OFF.
- RapidTwinning Error, incorrect 24V Phasing.
- RAPID GREEN / 1 AMBERLow flame sense current.
- Solid ONInternal control failure (ERR 18)
- Solid RedInternal gas valve circuit error (damaged furnace control)
- Solid Red (continuous reset)Continuous reset caused by an internal error (damaged…
- Solid STATUS (Red OFF)24VAC fuse open
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