REPLACEMENT BOARD ICM2812 – CONTROL BOARD

ICM Controls ICM2812 hot surface ignition furnace control board, published by ICM as a board-only replacement for the White-Rodgers 50M56U-843. It monitors ignition timing, trial for ignition, system switches, flame sensing and lockout. ICM now lists the ICM2812 under obsolete/legacy products and points to the ICM2812-KIT (board plus harnesses) for universal coverage.

Specifications published by the manufacturer. Source: manufacturer documentation.

Specs

• BrandICM Controls
• TypeHot surface ignition (HSI) furnace control board
• Control voltage24 VAC (18-30 VAC), 60 Hz
• Line voltage120 VAC, 60 Hz
• Ignitor output6 A at 120 VAC
• Gas valve output1.5 A at 24 VAC
• Motor outputsInducer 2.2 FLA at 120 VAC; blower 14.5 FLA at 120 VAC
• Operating range-40 to 175 F, 5-95% RH non-condensing
• NoteListed by ICM as legacy; ICM2812-KIT is the current universal option

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• 50M56U-843

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

How do I know the board is actually bad?

Most boards that get replaced were not the problem. Check the on-board fuse first (usually a 3 amp automotive blade), then the rollout and limit switches, the pressure switch and its hose, the flame sensor and the igniter. Then pull the fault history. Most controls from the last 20 years store the last four or five faults, and many have a recall button that scrolls them back. The legend is inside the blower door. If the board powers up, sequences and flashes a code at a switch, it is doing its job.

The 3 amp fuse keeps blowing. Do I need a board?

Almost never. A blown fuse means a short on the 24 volt side, and the most common by far is thermostat wire rubbed through where it crosses sheet metal, at a cabinet knockout or the condenser whip entry. Pull the thermostat wires off the board and the Y wire off the contactor, fuse it, and power up. If it holds, the fault is in the wiring.

Do the DIP switches matter?

Very much. Photograph every switch bank and wire before the old board comes out. Settings cover heat fan off delay (90, 120, 150 or 180 seconds), single or multi-stage stat, conventional or heat pump, and blower signal type. A wrong off delay reads like a bad board.

Is a control board a universal drop-in?

No. A communicating board (ComfortNet, Infinity, Evolution type) will not run a non-communicating system, and the reverse is true too. Stat, outdoor control and board must all speak the same language. Blower type matters too. PSC boards switch 120V speed taps, X13 boards send 24 volts to a torque input, variable speed boards send a serial signal. Boards are non-returnable once installed, so bring the model number in.