Heatcraft Unit Cooler Not Cooling? How to Read IntelliGen Alarm Codes Before You Start Swapping Parts

If a Heatcraft-equipped walk-in or reach-in is running warm, the fastest diagnostic path is the IntelliGen controller itself — not a part swap. The light bar tells you if something's wrong (solid yellow = evaporator error, red = active alarm), and the OLED display tells you what: an AL01 points to high box temperature, an AL06 flags a door left open, and an ER-series code narrows it down to a specific sensor or component before you pull a single wrench.

Below is a breakdown of the codes techs see most often on Heatcraft (Bohn, Larkin, Chandler) unit coolers, what typically causes each one, and the confirmed OEM parts that resolve the two failure points we see the most: contactor failure and evaporator fan failure.

What Do the IntelliGen Alarm Codes Mean?

The IntelliGen board (iRC) reports two types of messages: ER-codes (errors, usually sensor- or communication-related) and AL-codes (alarms, usually condition-based). Here are the ones most relevant to field troubleshooting:

An AL01 (High Box Temp) with no sensor errors underneath it almost always traces back to one of two things: the compressor/condenser circuit isn't engaging, or the evaporator isn't moving enough air across the coil. That's where the contactor and the evaporator fan assembly come in.

Unit Won't Start: Diagnosing a Failed Contactor

Direct answer: If the outdoor unit or condensing circuit fails to engage despite the IntelliGen calling for cooling, and you hear humming, buzzing, or chattering from the contactor cabinet instead of a clean pull-in, the 3-pole contactor has likely failed from contact pitting or coil burnout.

Definite-purpose contactors fail from ordinary wear: arcing across the contact surfaces, debris lodging between contacts, or coil burnout from voltage fluctuation. Once the contacts pit or weld, you'll see the system fail to short-cycle cleanly, or fail to start at all even though the thermostat/controller is calling for cooling.

Confirmed OEM part: Heatcraft 2259996 — 3-pole definite-purpose contactor, 208–240V coil, 25A rated. It's a direct OEM fit, so terminal position, lead wire length, and mounting footprint match without field modification — a real consideration since a mismatched universal contactor is a common source of repeat callbacks on commercial refrigeration circuits.

Coil Icing or Warm Box: Diagnosing Evaporator Fan Failure

Direct answer: If the box is running warm despite the compressor cycling normally, or you're seeing frost buildup on the evaporator coil, check the evaporator fan motor and blade before assuming a refrigerant issue — reduced airflow across the coil is one of the most common causes of both symptoms.

A weak or seized 1/15 HP evaporator motor, or a fan blade that's lost its pitch/balance, drops the CFM moving across the coil. That reduces heat transfer, which can show up as either a warm box (not enough cooling capacity reaching the space) or coil icing (the coil runs colder than it should relative to airflow, and frost accumulates faster than defrost cycles clear it).

Confirmed OEM parts:

• Heatcraft 25322406 — 1/15 HP evaporator fan motor, 208–230V single-phase, 1550 RPM, direct replacement for the discontinued 25322401. Used across Bohn, Larkin, and Chandler unit coolers with AO Smith/Century cross-compatibility.
• Heatcraft R026215300 — 10-inch, 5-blade evaporator fan blade, 40° pitch, CCW rotation (viewed from discharge side), 5/16" bore. Factory-weighted for balance — a mismatched blade pitch or blade count is a quiet cause of reduced airflow that doesn't throw an error code on its own.

Since the motor is sold as an assembly without the fan blade, inspect the existing blade for pitch deformation or imbalance any time you're replacing the motor — running a warped or wrong-pitch blade on a new motor just moves the airflow problem forward instead of solving it.

Box Reads Warm But Everything's Running: Diagnosing an AL06 Door Open Alarm

Direct answer: An AL06 alarm means the IntelliGen controller sees the door switch reporting open — either the door is physically open, the door switch itself has failed, or the switch wiring has come loose or corroded. It's a controller-input issue, not a refrigeration-cycle fault, so don't start diagnosing the compressor or evaporator until this is ruled out.

Walk through it in this order:

1. Confirm the door is actually closed and the gasket is sealing fully — a warped door or failed gasket can hold the switch in a partially-open state even when the door looks shut.
2. Check the door switch itself. A magnetic reed switch that's shifted out of alignment, or a mechanical plunger switch that's stuck or corroded, will report open even with the door closed.
3. Inspect the switch wiring back to the iRC board. Loose terminals, chafed insulation, or moisture intrusion at the switch connector are common causes on units that see frequent door cycling.

If the switch and wiring check out but AL06 persists, the alarm will typically also drive box temperature up over time (since an open door lets warm, humid air into the space) — at that point cross-check against AL01 (High Box Temp) rather than treating them as two separate problems.

No Communication From the Unit: Diagnosing ER25 and ER26 Connection-Lost Errors

Direct answer: ER25 (System Connection Lost) and ER26 (EV Connection Lost) both indicate the iRC board has stopped receiving communication from a component it expects to hear from — ER25 points to the broader system network, ER26 specifically to the electronic expansion valve. Neither code identifies a refrigerant or mechanical fault on its own; both are communication-layer errors.

Common causes, in the order worth checking:

• Loose or disconnected communication wiring at the board terminal or at the component end — the single most common cause of both codes on units that have been serviced recently.
• Power interruption to the affected component. If the EV driver or a networked sensor lost power (blown fuse, tripped breaker, disconnected harness), the board reports it as connection lost rather than a power fault.
• Board or UI failure. If wiring and power check out, the iRC board itself or the user interface module may need replacement — this is a less common cause but worth ruling in once the simpler checks are exhausted.

Because these are network-layer codes, don't assume a bad EV or bad sensor without first confirming the board is actually receiving a signal — replacing a mechanical component won't clear a communication error caused by a loose connector.

Frequently Asked Questions

What does an IntelliGen AL01 code mean on a Heatcraft unit cooler? AL01 indicates High Box Temp — the space isn't reaching setpoint. It's a symptom code, not a root cause, so check for AL04 (input fault) or ER-series sensor codes underneath it, then verify the contactor is engaging and the evaporator fan is moving normal airflow.

How do I know if my Heatcraft 2259996 contactor needs replacement? Watch for burnt or pitted contacts, a chattering or humming sound when the 208–240V coil tries to engage, or a condensing unit that fails to start despite a valid call for cooling. Any of those point to contact wear or coil failure on the existing contactor.

Can I run a lower-amperage or universal contactor in place of the 2259996? A higher amperage rating is generally acceptable from a safety standpoint, but coil voltage and physical footprint have to match the existing bracket. The OEM 2259996 guarantees lead wire length and terminal position align with Heatcraft equipment, which a generic substitute doesn't always do.

Is the 25322406 evaporator motor compatible with 115V systems? No — it's a dedicated 208–230V motor. Running it on 115V will cause it to fail to start or lose significant torque. Confirm line voltage at the terminal block before installing.

What rotation direction does the R026215300 fan blade need? CCW (counter-clockwise), viewed from the hub/discharge side. Confirm this against the motor's lead orientation before mounting — a blade installed backward moves air the wrong direction across the coil and will not fix an airflow-related alarm.

What does an AL06 alarm mean if the door is clearly closed? It means the controller still isn't receiving a "closed" signal from the door switch itself. Check the switch alignment or wiring before assuming it's a false alarm — a misaligned reed switch or a corroded connection will report open even when the door is sealed shut.

Does an ER25 or ER26 error mean the expansion valve or a sensor has failed? Not necessarily. Both are communication-layer errors — the board isn't hearing from the component, which is different from the component being defective. Check wiring, connectors, and power to the affected component first; replacing the EV or sensor won't fix a wiring or power issue underneath a connection-lost code.

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