Carrierfurnace

58MCA

40″ multipoise 90% · secondary HX bulletin era

Carrier / Bryant 40″ multipoise 90% family that Carrier SMB 09-0024 names: 58MCA / MCB / MXA / MXB / MSA / UVB / MVP / MVB / MVC / MTA / MTB and Bryant 340A / 340M / 345M / 350A / 350M / 351D / 352A / 352M / 355A / 355B / 355C / 355M. Serial range on that bulletin is 2993A00001 – 1808A99999. Two-digit or vintage LED depending on revision. Secondary HX restriction is the warranty story — not a 59TP6 model-plug call.

Not 59MN7 / 59TP6 / 59SC5 current 59-series. Those are outside SMB 09-0024. Not 58STA 80%. A Canadian dealer trade-in flyer naming 59MN7 is a different program — do not quote SMB 09-0024 on a 59-series serial.

Diagnose this model Install notes Board cross-ref Field wiring

Bulletin

Carrier SMB 09-0024 (issued 6/8/09, rev 12/17/12)

Serial range

2993A00001 – 1808A99999 on the published bulletin

Coverage

Secondary (condensing) HX · 20 years from original install on that SB

Distributor sheet

Carrier Enterprise heat-exchanger claims cheat sheet (Watsco)

This board

Vintage 90% IFC — LED flash or early two-digit. Confirm THIS door.

These cabinets predate current 59-series doors. Do not apply 59TP6 32-as-low-fire or Infinity ABCD.
Secondary HX restriction looks like pressure-switch lockout, rollout, or CO / combustion fail.
Inspection procedure is the dealer bulletin (DSB09-0022 / SMB 09-0022 language). Photograph the secondary and the serial before you quote warranty.

Write the live flash or two-digit. Serial number first — the bulletin is serial-gated.

Universal swap

Read the silk

Bulletin-era 90%. 50A55 / S9200U / 50M56U only if the silk is already that WR family — not because the cabinet says 58MCA.

Silk: 58MCA · 50A50 · 50A55

White-Rodgers

50A55-843
Only if the dead board is already a 50A50 / 50A55 carbide module.
50M56U-843
Harness kit when the silk is on the 50M56U single-stage HSI list.

ICM

—

Honeywell

S9200U1000
S9200U lists 50A55-843 and older Carrier 50A5x cousins. Not a current 59-series IFC.

A 59TP6 / 59MN7 IFC. Wrong generation.
Filing SMB 09-0024 on a current 59-series serial.

After you pull the dead card

1Kill power. Photograph the silk-screen part number on the dead board before you pull it.
2Match staging (1 vs 2 vs modulating), igniter (carbide / nitride / spark), and motor (PSC / ECMx / 9-speed tap / serial VS).
3Set heat-off delay and any 80+/90+ jumper to the door card. Prove one full try and flame µA before you leave.
4Serial first if this is an HX call — SMB 09-0024 is 2993A00001–1808A99999.

Field wiring

Written landings for Carrier 58MCA. Not a factory schematic.

Furnace · single-stage 24V

R / C / W / Y / GGas furnace

Conventional single-stage furnace IFC. One W. Cool Y passes through to the outdoor. No ComfortBridge, no ABCD, no W2.

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 → IFC → transformer → R120V in, 24V out
2Call. Stat W → IFC W~24 VAC
3Draft. IFC → inducer → PS close120V motor, 24V prove
4Ignite. IFC → HSI120 VAC
5Gas. IFC → valve~24 VAC
6Flame. Rod → IFCµA DC
7Blow. IFC → heat speedAfter flame prove

This indoor

Legacy 80% 58MCA class. 24V. SMB 09-0024 is serial-gated.

24V single-stage heat

Door card is one-stage. Twin terminal empty unless the job is actually twinned.

Wall thermostat

Single-stage heat/cool. W2 from a leftover two-stage stat does nothing useful.

R24V hot from the IFC24V
CCommon24V
WHeat24V
YCool — also starts the outdoor24V
GFan24V

Furnace IFC

Transformer lives here. Y out to the outdoor contactor. TWIN empty on a standalone.

RHot to the stat24V
CCommon — must reach the outdoor24V
WHeat call24V
YCool in / cool out24V
GBlower24V
TWINEmpty unless twinned24V

Landing

24VIFC Rstat R
~24 VAC hot
24VIFC Cstat Coutdoor C
Common
24VStat WIFC W
Heat. Stays in this cabinet.
24VStat YIFC Youtdoor Y
Cool / contactor
24VStat GIFC G
Fan. Does not go outdoors.

IFC harness — single-stage heat

After W arrives. This is the gas train, not the thermostat strip.

Transformer + fuse

120V primary. 24V secondary. Dark stat = fuse / door / transformer first.

L1 / N120V to the IFCLine
XFMR24V to R24V
FUSEOn the IFC24V

24V safety chain

Door, limit, rollout in series. Open anywhere kills heat.

DOORInterlock24V
LIMITMain limit — rise / no airflow24V
ROLLOUTManual reset. Do not jumper and leave24V

Inducer + one pressure switch

W → inducer 120V → PS closes → IFC continues. One hose, one switch.

IND120V from the IFC to the inducerLine
PS24V prove back to the IFC24V
HOSESingle hose. Do not add a second because two-stage boards have two.24V

HSI + single valve

Igniter is 120V from the IFC. Valve is 24V. Flame rod is µA DC back to the IFC.

HSI120V hot-surface igniter — not 24VLine
VALVE24V to the single solenoid24V
FLAMEµA DC on the rod. Not a 24V circuit24V

PSC blower + run cap

Heat / cool / park taps on the motor. The cap is on this blower — not the outdoor dual can.

HEATHeat speed tap24V
COOLCool speed tap24V
PARKUnused leads parked24V
CAPRun capacitor on the blowerCap

Landing

LineL1IFCinducer
120 VAC after W
24VIFCPSIFC
~24 VAC prove. Open PS = no ignition.
LineIFCHSI
120 VAC during trial
24VIFCgas valve
~24 VAC after flame prove starts
24VFlame rodIFC
µA DC. Not 24V.
LineIFCblower
120V tap + cap

Prove it

24 VAC from R to C at the IFC. Fuse / transformer first if the stat is dark.
W at the IFC under a heat call. Then inducer / igniter / valve per THIS door card.

Do not

Do not land a ComfortBridge 1/2 or Infinity ABCD pair on this IFC.
Do not hunt W2 / E8 / high-fire on a one-stage door.
TWIN must be empty on a standalone.

9-speed tap, PSC, and CT motors share this thermostat landing. The motor is on the IFC harness diagram.

Sequence

1
Serial
Read the full serial. SMB 09-0024 only names 2993A00001–1808A99999.
2
Combustion
Restriction in the polypropylene-coated secondary fails combustion / draft prove.
3
Warranty path
Dealer submits on the bulletin with the inspection certificate. Coupling box kit, cold-spot baffle, cell panels ride with the secondary.

Faults on this IFC

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

Draft / PS lockout

Will not prove / fails combustion

hazard

On this family that is often a restricted secondary, not a 59TP6 trap lecture alone.

1 Prove inducer and the live code
Do not pull power — that clears the Carrier 58MCA active code. Write Draft / PS lockout. Is the inducer spinning on this call? Silent inducer is not a pressure switch. Serial in 2993A00001–1808A99999? If no, this bulletin does not apply — treat as a standard 90% draft call.
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. Visual secondary / coupling box per the Carrier inspection sheet. Do not punch holes in the secondary to ‘test.’
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. Combustion analysis if it still fires. Failed CA + restriction = bulletin path.
Expect: Switch closes on known draft. Vent unrestricted.
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.

Limit / rollout

Overheat or flame containment

warn

Restricted secondary raises head and can open rollout / limit.

1 Treat this as flame outside the exchanger
Do not reset the Carrier 58MCA 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. Inspect the secondary before you replace a limit. Chimney-style thinking is wrong — these are 90% collectors.
Expect: Dry collector, open flue, trap clear.
3 Reset only after the cause is fixed
Manual-reset rollout. Recurring rollout on Carrier 58MCA is a CO / fire call — cracked primary, misaligned burners, or a failed secondary. Confirm CO in the space before you leave.
Expect: One clean cycle after the cause is fixed. No second reset as a repair.

Workflows

SMB 09-0024 path

58M / 340–355 90%, no heat or red-tagged secondary.

1 Prove the call and the live code
Photograph rating plate, serial, and the secondary / coupling box before you pull parts.
Expect: Write whatever Vintage 90% IFC — LED flash or early two-digit. Confirm THIS door. is showing. Write the live flash or two-digit. Serial number first — the bulletin is serial-gated.
If fail: No call at the IFC → stat / harness. Do not change gas parts.
2 Isolate the first failed step in the sequence
Confirm the model is on the SMB 09-0024 list and the serial is in 2993A00001–1808A99999.
Expect: Combustion: Restriction in the polypropylene-coated secondary fails combustion / draft prove.
3 Confirm with a number, then the next part
Coverage on that SB is 20 years from original install — not ‘lifetime’ and not current 59-series. Dealer claim: bulletin warranty, not a standard parts claim. Include coupling box kit, cold-spot baffle, cell inlet/outlet panels per the Carrier Enterprise cheat sheet. Option on some revisions was a credit toward a new Carrier/Bryant/Payne unit. Confirm what HVACPartners still honors — do not quote a dollar figure from a Canadian flyer as factory policy.
Expect: Serial: 2993A00001–1808A99999 for SMB 09-0024. Outside range = not this bulletin. · Secondary: Inspection per DSB09-0022 / SMB 09-0022 language. Photograph first.
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

Serial

2993A00001–1808A99999 for SMB 09-0024. Outside range = not this bulletin.

Secondary

Inspection per DSB09-0022 / SMB 09-0022 language. Photograph first.

Gotchas

59-series techs file this bulletin on a 2018 59TP6. The published model list is 58M / 340–355. Wrong claim.
Serial 1808A is calendar 2008-class, not 2018. Read Carrier week/year the way the bulletin prints it.
Bryant 355CAV on this list is not the current Evolution 880TA.

Related plates

Install this plate

Install Carrier 58MCA as 40″ multipoise 90% · secondary HX bulletin era.

40″ multipoise 90% · secondary HX bulletin era

This plate — not the sister SKU

Not 59MN7 / 59TP6 / 59SC5 current 59-series. Those are outside SMB 09-0024. Not 58STA 80%. A Canadian dealer trade-in flyer naming 59MN7 is a different program — do not quote SMB 09-0024 on a 59-series serial.
59-series techs file this bulletin on a 2018 59TP6. The published model list is 58M / 340–355. Wrong claim.
Serial 1808A is calendar 2008-class, not 2018. Read Carrier week/year the way the bulletin prints it.
Bryant 355CAV on this list is not the current Evolution 880TA.

IFC on this door

These cabinets predate current 59-series doors. Do not apply 59TP6 32-as-low-fire or Infinity ABCD.
Secondary HX restriction looks like pressure-switch lockout, rollout, or CO / combustion fail.
Inspection procedure is the dealer bulletin (DSB09-0022 / SMB 09-0022 language). Photograph the secondary and the serial before you quote warranty.

Hardware

Bulletin: Carrier SMB 09-0024 (issued 6/8/09, rev 12/17/12)
Serial range: 2993A00001 – 1808A99999 on the published bulletin
Coverage: Secondary (condensing) HX · 20 years from original install on that SB
Distributor sheet: Carrier Enterprise heat-exchanger claims cheat sheet (Watsco)

First fire

1Photograph rating plate, serial, and the secondary / coupling box before you pull parts.
2Confirm the model is on the SMB 09-0024 list and the serial is in 2993A00001–1808A99999.
3Coverage on that SB is 20 years from original install — not ‘lifetime’ and not current 59-series.
4Dealer claim: bulletin warranty, not a standard parts claim. Include coupling box kit, cold-spot baffle, cell inlet/outlet panels per the Carrier Enterprise cheat sheet.
5Option on some revisions was a credit toward a new Carrier/Bryant/Payne unit. Confirm what HVACPartners still honors — do not quote a dollar figure from a Canadian flyer as factory policy.
6Current 59MN7 / 59TP6 / 59TN6 are NOT on SMB 09-0024. Do not file them on this bulletin.

Do not on Carrier 58MCA

Not 59MN7 / 59TP6 / 59SC5 current 59-series. Those are outside SMB 09-0024. Not 58STA 80%. A Canadian dealer trade-in flyer naming 59MN7 is a different program — do not quote SMB 09-0024 on a 59-series serial.
59-series techs file this bulletin on a 2018 59TP6. The published model list is 58M / 340–355. Wrong claim.
Serial 1808A is calendar 2008-class, not 2018. Read Carrier week/year the way the bulletin prints it.

Maker literature

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

Carrier residential furnacesLiterature searchProduct pages carry current literature. I/O booklets are typically HVACpartners / dealer.Open manufacturer PDF
Carrier HVAC resourcesLiterature searchOwner-facing literature hub. Do not invent a 59-series I/O URL.Open manufacturer PDF
Carrier residential furnacesLiterature searchSearch Carrier 58MCA 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

SMB 09-0024
serial-gatedUS
40″ multipoise 90% secondary heat exchanger — serial-gated coverage
2009-06-08 (rev 2012-12-17)
Serial 2993A00001 – 1808A99999
Secondary (condensing) heat exchanger on 58M / Bryant 340–355 family · Serial-gated parts coverage
Open facts Open manufacturer PDF
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
CE Canada Bryant trade-in 2025–26
ended seasonCanada
High-efficiency gas furnace trade-in — Bryant Canada
2025-04 (ended 2026-04-30)
Failed 340–355 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