Carrierfurnace

59TN6

Infinity · two-stage · communicating 96%

Infinity two-stage communicating 96% furnace (Bryant 986T). ABCD bus plus a two-stage gas valve and dual pressure switches. Not modulating like 59MN7. Two-digit board codes plus Infinity English on the wall control. 31/32 here are low vs high PS — the same two-stage physics as 59TP6, on a communicating control.

Not 59MN7 (modulating % — pressure BAND, not discrete 31/32). Not 59TP6 (24V Performance — no ABCD, model-plug VS). Swapping an Infinity stat onto a 59TP6 does not make it a 59TN6. Not 59SC5 Comfort single-stage.

Diagnose this model Install notes Board cross-ref Field wiring

AFUE

96% condensing two-stage

Staging

Two-stage gas valve · two-speed inducer · dual pressure switches

Bus

Infinity ABCD wall control — capacity request is serial, valve is still two-stage

Blower

Infinity VS ECM

Sister SKU

Bryant 986T

This board

Infinity IFC + two-digit codes (two-stage, not modulating)

Infinity wall control Service / Last 10 events first — English names. Board two-digit still flashes 24, 31, 32, 33, 13, 34, 14, 41.
31/32 are discrete low vs high pressure switches. That is the opposite of 59MN7, where 31/42 is a band.
ABCD polarity, one Infinity control, C required. Do not land a 24V stat on ABCD.
A 59TP6 door card is the wrong card: same 31/32 words, different bus and no model-plug CFM readout.

Infinity event history primary. Board last-status button if the wall control is blank.

Universal swap

No universal

Infinity two-stage. No universal.

Silk: Infinity

White-Rodgers

—

ICM

—

Honeywell

—

Any 50A55-843 / 50A65-843 / 50M56U-843 / 50M56X-843 / S9200U1000 universal — those are conventional 24V HSI, not this data bus.
ICM280 / 2811 / 2810 / 282B — wrong IFC family.
59TP6. 59MN7 modulating card.

After you pull the dead card

1OEM Infinity two-stage IFC. Pair the ABCD bus.

Field wiring

Written landings for Carrier 59TN6. Not a factory schematic.

Infinity / Evolution furnace

ABCDGas furnace

59MN7 / 59TN6 / 987M / 986T class. Four-wire communicating furnace. D is 24V hot, not W and not Y.

Written circuit description only — FieldBench does not redraw maker schematics. Example: R to W closes on a heat call; verify 24V at W1 before you change the IFC.

Open manufacturer PDF

Heat sequence

1Power. L1 / N → IFC120V
2Call. Data pair or 24V W → IFCBus or 24V
3Draft. IFC → inducer → proveTwo-stage PS or a pressure band
4Ignite. IFC → HSI → valve120V igniter
5Blow. IFC → serial ECMNo tap, no cap

This indoor

Infinity two-stage 96%. Same ABCD, two-stage valve.

ABCD only

Infinity or Evolution wall control and a matching outdoor.

Infinity / Evolution control

A/B data, C common, D 24V hot.

ADataData
BDataData
C24V common24V
D24V hot — not W24V

Infinity / Evolution IFC

Same ABCD. Do not convert it to 24V by landing W and walking away.

ADataData
BDataData
CCommon24V
D24V hot24V

Landing

DataStat A/BIFC A/Boutdoor A/B
Data
24VStat C/DIFC C/D
24V common / hot. D is not Y or W.

IFC harness — communicating two-stage

Call arrives on the data pair (or 24V W). Gas train is still inducer / prove / igniter / valve.

Transformer + fuse

24V still exists for accessories and for a 24V outdoor. Data pair is not the transformer.

L1 / N120VLine
R / C24V strip24V
FUSEOn the IFC24V

24V safety chain

Limit / rollout / door still open the heat path. Codes are on THIS IFC language.

DOORInterlock24V
LIMITMain limit24V
ROLLOUTManual reset24V

Two-speed inducer + dual PS

Low vs high prove. Do not tee the hoses. Do not apply this to a modulating cousin.

IND LO/HITwo-speed inducerLine
LPSLow prove24V
HPSHigh prove24V

HSI + two-stage valve

Two solenoids or a two-stage valve. Staging is the bus or W1/W2, not a tap.

HSI120V igniterLine
MV / HV24V low / high solenoids24V
FLAMEµA DC24V

Serial variable-speed ECM

IFC talks to the motor on the serial harness. No F-taps. No dual run cap on this blower.

SERIALIFC-to-motor harness. Unplugged motor = CFM / comm fault, not a tap problem24V
CFMSet in the IFC menu / model plug / CoolCloud — not a dip switch on most of these24V

Landing

LineCallIFCinducerprove
Low then high
LineIFCHSIvalve
120V igniter, 24V or serial valve
24VFlame rodIFC
µA DC
DataIFCserial blower
No F-taps. No PSC cap.

Prove it

Wall-control equipment list. The furnace and outdoor both present.
ABCD polarity. C still required.

Do not

Do not land W on a spare screw to make it 24V.
A 926T / 59TP6 / 59SC5 is the other diagram.

ABCD is the published Infinity / Evolution control.

Sequence

1
Call
Infinity wall control requests low or high heat over ABCD. IFC runs the two-stage sequence — there is no modulating %.
2
Low fire
Inducer low → low PS must close (31/32 family) → HSI → low-fire solenoid → flame (34 if no prove) → VS blower per Infinity CFM.
3
High fire
Inducer high → high PS must close. 32 on this furnace is low-fire draft, not a 59MN7 band miss.
4
Limit / ign
33 → 13 limit lockout. 34 → 14 ignition lockout. Same Carrier two-digit hardening as TP6.

Faults on this IFC

Step 1, then 2, then 3. Expected reading and the fail branch sit under each check.

ABCD

Communication

lockout

Wall control or outdoor dropped off the bus.

1 Data pair, not 24 V
On Carrier 59TN6 indoor/outdoor comm is a data pair (AB, S1/S2, U, ComfortBridge, ComfortLink — whatever THIS plate uses). It is not a 24 V Y. Check polarity, continuity, and that nobody landed it on R/C. A/B/C/D landing, polarity, only one Infinity control, no 24V on D.
Expect: Pair continuous, not shorted to chassis, polarity per the diagram.
2 Power both ends, then the outdoor status
Indoor transformer and outdoor control both alive. Read the outdoor LED / 7-seg. Water in the outdoor control is the usual dead-end after a storm. C present. A 24V Performance stat on this IFC will not stage it like a 59TP6.
Expect: Both controls powered. Outdoor showing a comm or address state, not a blank board.
3 Address / bias, then the control
Communicating plates need a matching indoor address and sometimes a terminating bias. Swap is last: known-good pair + power both ends + correct address. Outdoor pair on the same bus — a dead Greenspeed looks like indoor comm loss until you read events.
Expect: Indoor sees the outdoor. No comm code after a power cycle.

Secondary fuse open

warn

24 V fuse on the IFC.

1 Find the 24 V short before you replace the fuse
On Carrier 59TN6 an open IFC fuse is a short on W, Y, G, HUM, EAC, or a data pair landed on 24 V. Unplug the thermostat / data harness first. HUM/EAC, valve harness, or 24V landed on ABCD.
Expect: Fuse out. 24 V transformer still good. Harness isolated.
2 Replace the fuse with the harness off
New fuse, harness still off. If it holds, the short is in the field wiring or accessory. Plug one circuit back at a time (W, then Y, then HUM/EAC). Replace fuse only after the short is gone.
Expect: Fuse holds with harness off. Dies when the shorted lead lands.
3 If it blows with the harness off
Short is on the Carrier 59TN6 IFC or the gas-valve harness. Unplug the valve and try once more. Repeat blow with valve unplugged = IFC.
Expect: Do not keep feeding fuses into a welded valve coil or a burned IFC trace.

31 / 32

Low vs high pressure switch

lockout

Two-stage draft path. 31 is the active-stage / draft prove; 32 is low-fire PS. Unlike 59MN7, these are discrete switches.

1 Prove inducer and the live code
Do not pull power — that clears the Carrier 59TN6 active code. Write 31 / 32. Is the inducer spinning on this call? Silent inducer is not a pressure switch. Two hoses, two switches. Do not treat this as a modulating band.
Expect: 120 VAC at the inducer on a heat call. Wheel turning.
If fail: 120 VAC missing → IFC / door switch / incoming power. Voltage + dead motor → inducer.
If pass: Inducer running + this code → trap, hose, switch, vent (step 2).
2 Trap, collector, and the hose
A drowned 96% trap will not make collector pressure. Pull the trap, flush it, confirm the collector box and inducer outlet are not full. Hose cracked, off the port, or full of water fakes an open switch. 32 = low-fire hose, low inducer, attic PVC/trap/wind.
Expect: Trap flowing, hose dry and downhill, ports not swapped on a two-switch board.
3 Switch ohms, then vent load
Ohm the pressure switch: NO, must close when that inducer speed is making the collector setpoint. If the switch is good, walk the PVC — bird screen, ice, long 2" run, wind, shared chase. High-fire prove fail is the high PS, not a 59MN7 42 band story.
Expect: Pressure switches: Two discrete switches. 32 = low. High-fire has its own hose. Not an MN7 band.
If fail: Replace the open switch only after the vent and trap are proven.
If pass: Switch closes on draft and the code stays → IFC input.

33 / 13

Limit or rollout

warn

Airflow or flame-containment. 13 is the hardened 33.

1 Treat this as flame outside the exchanger
Do not reset the Carrier 59TN6 rollout and walk away. Write the code, kill the call, and look for flame at the burners, crossover, and vestibule before you do anything else.
Expect: No flame outside the exchanger. Burners seated. Crossover lit.
If pass: Still inspect secondary / flue / condensate before you reset.
2 Secondary, condensate, and flue
Blocked secondary, drowned collector, or a plugged flue pushes flame out the front. Pull the inducer/collector look, confirm the trap is flowing, and check PVC/vent. Infinity heat CFM, filter, coil, return. Not a 59SC5 heat tap and not a 59TP6 model plug.
Expect: Dry collector, open flue, trap clear.
3 Reset only after the cause is fixed
Manual-reset rollout. Recurring rollout on Carrier 59TN6 is a CO / fire call — cracked primary, misaligned burners, or a failed secondary. Confirm CO in the space before you leave. Rollout is manual reset — inspect exchanger first.
Expect: One clean cycle after the cause is fixed. No second reset as a repair.

34 / 14

Ignition prove fail

lockout

Trial without flame sense. 14 is the hardened 34.

1 Measure µA while it is running
Do not clean first and guess. Series-µA the rod on Carrier 59TN6 during a call. Falling µA is oxide, ground, or a dying flame. A hard drop is often the pressure switch or limit opening, not the rod. HSI, gas, rod, ground.
Expect: Flame sense: µA per 59TN6 / 986T door card.
2 Rod, ground, then gas
Clean the rod with a non-scratch pad — not sandpaper. Chassis ground to burner box and IFC (painted screw and missing star washer are classic). Then manifold on the stage that is dropping and confirm LP conversion leftovers. If 32 is also stored, fix low-fire draft before you condemn the igniter.
Expect: Manifold on the rating plate. Solid burner-box ground.
3 Prove it is not a switch opening
Watch the live Carrier 59TN6 display when flame drops. A PS or limit code that appears at the drop means the rod was a victim. Inducer, hose, vent wind, or a limit on a wrong heat tap.
Expect: µA stable and the live code stays a flame code — then rod/valve/IFC. Otherwise chase the new code.

Blower RPM out of band

lockout

Infinity VS motor not at commanded CFM.

1 Is the wheel free?
Spin the Carrier 59TN6 blower by hand. Ice, debris, or a seized bearing is not a control problem. Confirm the motor type on this plate — serial ECM, 9-speed tap, or X-13 — before you grab a capacitor. Static, wheel, serial harness, Infinity indoor size / CFM setup.
Expect: Wheel free. Correct motor family for this IFC.
2 Command vs rotation
Call for G or heat and confirm the IFC is actually requesting CFM (taps, serial, or communicating). Amp the motor. Locked rotor + a good command = motor. No command = IFC / harness / shared data. Filter and coil.
Expect: Command present. Motor amps in range, not locked.
3 Static and the wrong motor
High static will trip current/limit codes and look like a dead motor. Measure TES vs this cabinet. Wrong horsepower or a leftover memory card after a control swap is the other half of this call.
Expect: Static on the blower chart. Matching motor / shared-data card.

Workflows

Identify TN6 vs MN7 vs TP6

Badge is gone or the last invoice just says ‘Infinity 96.’

1 Prove the call and the live code
ABCD bus present? No → 59TP6 / 59SC5, not this page. Yes → Infinity, continue.
Expect: Write whatever Infinity IFC + two-digit codes (two-stage, not modulating) is showing. Infinity event history primary. Board last-status button if the wall control is blank.
If fail: No call at the IFC → stat / harness. Do not change gas parts.
2 Isolate the first failed step in the sequence
Valve and PS: two-stage body + two discrete pressure switches = 59TN6. Modulating valve + transducer / band (no 32 low-fire switch) = 59MN7.
Expect: Low fire: Inducer low → low PS must close (31/32 family) → HSI → low-fire solenoid → flame (34 if no prove) → VS blower per Infinity CFM.
3 Confirm with a number, then the next part
59TP6 has the two-stage hardware but a 24V stat and a model plug. Putting an Infinity wall control on a 59TP6 does not make it a 59TN6. Bryant 986T = this chart. Bryant 987M = 59MN7. Bryant 926T = 59TP6.
Expect: ABCD: Communicating. D is not W. C required. · Pressure switches: Two discrete switches. 32 = low. High-fire has its own hose. Not an MN7 band.
If fail: Stay on this plate. The out-of-range reading is the part.
If pass: Reading in range → the next step in this workflow is the repair.

Infinity no-heat

Wall control is on, house is cold, or the homeowner says the system ‘lost communication.’

1 Prove the call and the live code
Infinity event list first. English text beats guessing the two-digit.
Expect: Write whatever Infinity IFC + two-digit codes (two-stage, not modulating) is showing. Infinity event history primary. Board last-status button if the wall control is blank.
If fail: No call at the IFC → stat / harness. Do not change gas parts.
2 Isolate the first failed step in the sequence
Then the board: 24 fuse, ABCD drop, 31/32 draft, 34 ignition, 33 limit.
Expect: Low fire: Inducer low → low PS must close (31/32 family) → HSI → low-fire solenoid → flame (34 if no prove) → VS blower per Infinity CFM.
3 Confirm with a number, then the next part
C still required. Blank or rebooting control with 0 VAC at C is not a bad IFC. Do not convert to 24V by jumping W. You will not get a fair two-stage Infinity sequence.
Expect: ABCD: Communicating. D is not W. C required. · Pressure switches: Two discrete switches. 32 = low. High-fire has its own hose. Not an MN7 band.
If fail: Stay on this plate. The out-of-range reading is the part.
If pass: Reading in range → the next step in this workflow is the repair.

32 low fire on communicating two-stage

Inducer runs, no light-off, or it never leaves low heat.

1 Prove the call and the live code
32 on 59TN6 is low-fire PS — same physics as 59TP6, different bus. It is not a 59MN7 pressure band.
Expect: Write whatever Infinity IFC + two-digit codes (two-stage, not modulating) is showing. Infinity event history primary. Board last-status button if the wall control is blank.
If fail: No call at the IFC → stat / harness. Do not change gas parts.
2 Isolate the first failed step in the sequence
Low-fire hose only. Trap, collector, attic PVC, intake wind/ice.
Expect: Low fire: Inducer low → low PS must close (31/32 family) → HSI → low-fire solenoid → flame (34 if no prove) → VS blower per Infinity CFM.
3 Confirm with a number, then the next part
Confirm the inducer actually went to low, not a failed high-speed request wearing a 32. Then ignition (34). A starved low-fire prove will never give a clean 34 test.
Expect: ABCD: Communicating. D is not W. C required. · Pressure switches: Two discrete switches. 32 = low. High-fire has its own hose. Not an MN7 band.
If fail: Stay on this plate. The out-of-range reading is the part.
If pass: Reading in range → the next step in this workflow is the repair.

Test points

ABCD

Communicating. D is not W. C required.

Pressure switches

Two discrete switches. 32 = low. High-fire has its own hose. Not an MN7 band.

Flame sense

µA per 59TN6 / 986T door card.

Gotchas

Same ABCD plug as 59MN7. Wrong chart if you treat 31 as a modulating band.
Same two-stage gas as 59TP6. Wrong chart if you look for a model plug and a 24V W2.
Bryant 986T is the badge twin. 987M is the modulator.

Related plates

Install this plate

Install 59TN6 as Infinity two-stage 96%. ABCD + discrete 31/32. Twin of Bryant 986T / 987T.

Cat IV PVC · two-stage · dual PS · Infinity ABCD

Bus vs stages

Infinity control required. Two-stage valve — not 59MN7 modulation.
31/32 are discrete stage proves, like 59TP6, on an ABCD bus like 59MN7.

First fire

1Pair Infinity. Low stage then high stage. Both PS hoses.

Do not on Carrier 59TN6

Do not apply 59MN7 pressure-band commissioning.
Do not treat 59TP6 24V as this bus.

Maker literature

FieldBench does not host manufacturer files. Each link opens the maker’s own literature page in a new tab.

59TN6 product pageProduct pageOpen manufacturer PDF
Carrier residential furnacesLiterature searchProduct pages carry current literature. I/O booklets are typically HVACpartners / dealer.Open manufacturer PDF
Carrier residential furnacesLiterature searchSearch Carrier 59TN6 on the maker’s literature page.Open manufacturer PDF

Warranty and bulletins

Affected models, serial range, symptom, remedy, date. Maker files open on the manufacturer site.

All bulletins

Distributor HX claims sheet
dealerUS
Furnace heat exchanger claims — serial in/out of range
Serial 2993A00001 – 1808A99999 (in-range); later serials are standard warranty
Primary or secondary heat exchanger failure · Distributor claim path
Open facts Open manufacturer PDF
CE Canada HX guide
dealerCanada
Canada furnace heat exchanger claim options
2023-02-20
Heat exchanger failure — Canada · Canada distributor program
Open facts Open manufacturer PDF
CE Canada trade-in 2025–26
ended seasonCanada
High-efficiency gas furnace trade-in — Carrier Canada
2025-04 (ended 2026-04-30)
Failed 58M-family secondary within 20 years of install · Trade-in (ended)
Open facts Open manufacturer PDF
Residential limited warranty
warranty sheet
Carrier / Bryant registered heat-exchanger terms
Current 59-series / Evolution / Preferred registered warranty · Limited warranty certificate
Open facts Open manufacturer PDF
Dealer portals
dealer
Where remaining service letters live
Current-year service letters not on a public literature page · Maker dealer portal
Open facts Open manufacturer PDF