DM97MC

Display showing a firing percent or a run word is status.

1. 1 Confirm this is not a fault

   On the Daikin DM97MC this readout (% / run status) is run status, not a lockout. Write what the display actually shows and whether W/Y/G is present at the IFC.

   Expect: Idle / Ht / CF / stage+CFM words change when you apply and remove the call.

   If fail: If the word never changes on a real call, the call is not reaching this IFC.

   If pass: The board is alive. Diagnose the comfort complaint, not this code.

2. 2 Prove the call at the board

   Measure R to W / Y / G at the Daikin DM97MC IFC, not at the thermostat. Communicating plates need the data pair and a live indoor address — 24 V on W is not the test.

   Expect: Do not treat a low percent as a lockout. The stat asked for that rate.

   If fail: Fix the stat, harness, or data pair before you change parts.

3. 3 Watch one full sequence

   Leave power on. Watch ComfortNet / Daikin One modulating IFC through one cycle and write the first real fault that replaces this status word.

   Expect: Call: Communicating stat requests a % capacity. Valve and inducer modulate; blower CFM follows. There is no W2 solenoid to wait on.

Ignition retries exceeded at the commanded rate.

1. 1 Measure µA while it is running

   Do not clean first and guess. Series-µA the rod on Daikin DM97MC 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. Full try at the percent it is attempting. A valve that will not come off minimum looks like E0/E6.

   Expect: Typically ≥ 1.0 µA DC on this family — confirm the door card. Rising while running.

2. 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. Gas supply, HSI, rod, ground.

   Expect: Manifold on the rating plate. Solid burner-box ground.

3. 3 Prove it is not a switch opening

   Watch the live Daikin DM97MC 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.

Limit string open. VS should have been ramping with percent fire.

1. 1 Treat this as flame outside the exchanger

   Do not reset the Daikin DM97MC 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. 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. IFC heat CFM / modulating airflow table, not a tap and not DM96VC ‘high stage.’ Filter, coil, static. Rollout is still manual-reset hazard.

   Expect: Dry collector, open flue, trap clear.

3. 3 Reset only after the cause is fixed

   Manual-reset rollout. Recurring rollout on Daikin DM97MC 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.

Flame sense with the modulating valve de-energized.

1. 1 Shut the gas cock first

   On Daikin DM97MC the rod sees flame with the valve de-energized. Shut the cock. If flame stays, the valve is leaking — replace it. Do not jump or energize it as a test. Shut the cock. Leaking or slow-close valve.

   Expect: Flame dies when the cock is shut.

   If fail: Leaking valve. Replace. Do not leave the unit.

2. 2 Rod and IFC flame circuit

   If flame dies with the cock shut, the rod is shorted to ground or the IFC flame circuit is lying. Unplug the rod, inspect ceramic, and check the harness for a rub-through on the collector.

   Expect: Rod isolated from ground. IFC does not report flame with the rod unplugged.

3. 3 Confirm valve solenoids are actually off

   Measure 24 VAC at both solenoids after the call drops. A welded IFC relay or a shorted W will keep a solenoid wet and look like ‘unexpected flame.’ Replace the IFC only after the valve and rod are proven.

   Expect: 0 VAC at both solenoids after the call. No flame.

24 V fuse open.

1. 1 Find the 24 V short before you replace the fuse

   On Daikin DM97MC 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. Data pair shorted to R/C, HUM/EAC, valve harness.

   Expect: Fuse out. 24 V transformer still good. Harness isolated.

2. 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).

   Expect: Fuse holds with harness off. Dies when the shorted lead lands.

3. 3 If it blows with the harness off

   Short is on the Daikin DM97MC 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.

µA below threshold while firing.

1. 1 Measure µA while it is running

   Do not clean first and guess. Series-µA the rod on Daikin DM97MC 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. Rod, ground, manifold at the percent it is running — not a single two-stage high-fire number.

   Expect: Typically ≥ 1.0 µA DC on this family — confirm the door card. Rising while running.

2. 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.

   Expect: Manifold on the rating plate. Solid burner-box ground.

3. 3 Prove it is not a switch opening

   Watch the live Daikin DM97MC 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.

HSI circuit or equipment ground.

1. 1 Ohms at the igniter, then at the IFC

   On Daikin DM97MC measure cold ohms at the igniter plug, then at the IFC connector. An open at the plug is the element or local harness. Open only at the IFC is the harness rub-through on the collector. Ohms, 120 VAC during trial, ground screw.

   Expect: Nitride cold ohms per THIS door sticker — do not use an 80% Norton chart.

2. 2 120 VAC during warm-up

   Call for heat and measure 120 VAC at the igniter during the warm-up window. 0 V + good ohms = IFC igniter relay. Voltage + no glow = cracked nitride.

   Expect: 120 VAC only during warm-up. Visible glow before the valve opens.

3. 3 Do not keep cycling a cracked element

   A cracked nitride can ohm ‘good’ cold and open hot. If ohms and voltage are good and there is no glow, replace the igniter. Confirm polarity/ground (this plate’s polarity code) before you condemn a new igniter.

   Expect: One clean light after a known-good igniter and a proven ground.

L1/N or chassis ground.

1. 1 Hot and neutral at the IFC, not the disconnect

   On Daikin DM97MC polarity/ground is measured at the board. A correctly landed disconnect with a swapped whip at the IFC still throws this. Hot/neutral at the IFC.

   Expect: L1 hot, N neutral, ~120 VAC L1 to N, ~0 VAC N to ground.

2. 2 Burner-box and IFC ground

   Green ground to cabinet and IFC. Painted screw and missing star washer fail the ground check and kill flame sense.

   Expect: Near-zero ohms burner box to IFC ground screw.

3. 3 Then flame and HSI

   Polarity/ground faults take out HSI and flame sense together. After the wiring is right, run one heat cycle and confirm µA and igniter glow before you change those parts.

   Expect: Code cleared. One clean light. µA in range.

Daikin One / ComfortNet dropped, or internal / line-voltage on some dates.

1. 1 Data pair, not 24 V

   On Daikin DM97MC 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. Data pair, one master, outdoor on the same bus.

   Expect: Pair continuous, not shorted to chassis, polarity per the diagram.

2. 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. Same wiring rules as DM96VC — the valve type does not change the bus.

   Expect: Both controls powered. Outdoor showing a comm or address state, not a blank board.

3. 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.

   Expect: Indoor sees the outdoor. No comm code after a power cycle.

Serial ECM not running when commanded.

1. 1 Reseat the serial plug

   On Daikin DM97MC this is a communicating / serial ECM, not a tap motor. Kill power, reseat the 14-pin (or OEM serial plug) at the motor and at the IFC. Pins straight, no corrosion. Harness, wheel, motor. Not a tap motor.

   Expect: Plug fully seated both ends. Correct motor for this cabinet.

2. 2 Power and the data pair at the motor

   Line voltage at the motor, then the serial/data pair continuity. A half-seated plug or a pinched harness throws comm on a good motor.

   Expect: Line voltage present. Data pair not shorted to chassis.

3. 3 Motor vs IFC serial driver

   Known-good motor still throws this code = Daikin DM97MC IFC serial driver. Known-good IFC still throws it = motor module. Do not put a PSC or 9-speed tap motor on a serial IFC.

   Expect: One clean CFM request after a known-good pair.

Lost serial comms with the circulator.

1. 1 Reseat the serial plug

   On Daikin DM97MC this is a communicating / serial ECM, not a tap motor. Kill power, reseat the 14-pin (or OEM serial plug) at the motor and at the IFC. Pins straight, no corrosion. Harness, motor, IFC.

   Expect: Plug fully seated both ends. Correct motor for this cabinet.

2. 2 Power and the data pair at the motor

   Line voltage at the motor, then the serial/data pair continuity. A half-seated plug or a pinched harness throws comm on a good motor.

   Expect: Line voltage present. Data pair not shorted to chassis.

3. 3 Motor vs IFC serial driver

   Known-good motor still throws this code = Daikin DM97MC IFC serial driver. Known-good IFC still throws it = motor module. Do not put a PSC or 9-speed tap motor on a serial IFC.

   Expect: One clean CFM request after a known-good pair.

Motor HP does not match this DM97MC shared data.

1. 1 Read the plug / card on THIS cabinet

   On Daikin DM97MC the model plug or shared-data card must match this cabinet size. A 100 kBtu plug in an 80 cabinet overfires and limits. A leftover memory card after a control swap throws d0/d4-class codes. Do not load a DM96VC or AMVC96 card into this cabinet.

   Expect: Plug / card part matches the rating plate and the replacement control bulletin.

2. 2 Reseat, then confirm the menu

   Kill power, reseat, restore power. On communicating plates open the setup and confirm unit size / motor HP. Correct memory card / learn for DM97MC0603BN-class SKU.

   Expect: IFC recognizes the plug. No size-mismatch code.

3. 3 Do not run it mismatched

   A wrong plug is not a ‘temporary’ fix. It will throw limit, ignition, or blower-band codes that look like bad parts. Fit the correct plug, then re-run the original complaint.

   Expect: One clean sequence on the correct identity.

No shared data on a communicating setup.

1. 1 Read the plug / card on THIS cabinet

   On Daikin DM97MC the model plug or shared-data card must match this cabinet size. A 100 kBtu plug in an 80 cabinet overfires and limits. A leftover memory card after a control swap throws d0/d4-class codes. Memory card / learn. Empty network if someone landed data wires with no Daikin One / outdoor.

   Expect: Plug / card part matches the rating plate and the replacement control bulletin.

2. 2 Reseat, then confirm the menu

   Kill power, reseat, restore power. On communicating plates open the setup and confirm unit size / motor HP.

   Expect: IFC recognizes the plug. No size-mismatch code.

3. 3 Do not run it mismatched

   A wrong plug is not a ‘temporary’ fix. It will throw limit, ignition, or blower-band codes that look like bad parts. Fit the correct plug, then re-run the original complaint.

   Expect: One clean sequence on the correct identity.

On this modulator these letters are a prove-band / inducer path, not DM96VC low-vs-high discrete switches. Confirm on the DM97MC door card.

1. 1 Prove inducer and the live code

   Do not pull power — that clears the Daikin DM97MC active code. Write E1 / E2 / E8 / E9. Is the inducer spinning on this call? Silent inducer is not a pressure switch. Trap, PVC, inducer still matter — 97% still drowns a collector.

   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. 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. Do not replace ‘the high-fire PS’ as if this were two-stage.

   Expect: Trap flowing, hose dry and downhill, ports not swapped on a two-switch board.

3. 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. If the card in THIS cabinet maps them differently, the sticker wins.

   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.