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Error code reference

Thermador Refrigerator Error Code 4 Flashes

Compressor failure detected by the inverter board.

Thermador codesThermador refrigerator codes

Compressor failure detected by the inverter board.

First step from the service manual

Check all wires and connections first; verify compressor windings (6-7 ohms).

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What 4 Flashes means on a Thermador refrigerator

The 4 Flashes error code on a Thermador refrigerator indicates that the inverter board has detected a compressor failure. The inverter board is responsible for controlling the variable-speed compressor by regulating voltage and frequency output. When the inverter board senses an abnormal electrical condition from the compressor, such as a short, open winding, or overload condition, it shuts down operation and signals the fault through this flash sequence. This protects both the compressor and the inverter board from further damage.

The diagnostic process begins with a thorough inspection of all wiring and connectors between the inverter board and the compressor. Loose pins, corroded terminals, or damaged wire insulation can cause intermittent or false fault readings. If connections are secure and undamaged, the next step is measuring the compressor winding resistance. A properly functioning compressor should measure approximately 6 to 7 ohms across its windings. Readings significantly outside this range indicate an internal compressor fault.

If winding resistance is within spec and connections are intact, the inverter board itself may be the source of the fault. Inverter boards can develop internal failures that cause them to misread compressor signals or fail to deliver proper drive voltage. In some cases, a compressor may test within normal resistance values at room temperature but fail under load due to thermal breakdown of internal insulation. This makes load testing and careful observation during startup an important part of a complete diagnosis.

Source: manufacturer service documentation.

Common causes of 4 Flashes

  1. 01

    Loose or corroded wiring connections

    Wiring / connection

    Poor connections between the inverter board and compressor can interrupt the signal and trigger a false fault. Inspect all connectors for corrosion, bent pins, or loose terminal fits before replacing any components.

  2. 02

    Failed compressor windings

    Part replacement

    Internal compressor winding failure causes resistance readings outside the 6 to 7 ohm specification. Readings near zero indicate a short, while very high or open readings indicate a broken winding, both requiring compressor replacement.

  3. 03

    Faulty inverter board

    Part replacement

    The inverter board may develop internal component failures that cause it to incorrectly detect a compressor fault or fail to properly drive the compressor. This is suspected when wiring and compressor winding resistance both test within normal range.

  4. 04

    Compressor thermal overload

    Wiring / connection

    A compressor that is overheating may trip its internal thermal protector, causing the inverter board to register a failure. This can result from poor ventilation around the unit or a refrigerant issue causing excessive head pressure.

  5. 05

    Damaged compressor wiring harness

    Part replacement

    Chafed or broken wiring in the harness running to the compressor can cause intermittent open or short circuits. Visually trace the full length of the harness and flex each section while monitoring for resistance changes.

See the test procedure for each cause

Frequently asked questions about 4 Flashes

What does 4 Flashes mean on a Thermador refrigerator?
The 4 Flashes code means the inverter board has detected a compressor failure. The inverter board monitors the compressor's electrical characteristics and shuts the system down when it senses an abnormal condition. This fault protects the compressor and control electronics from further damage. A technician will need to inspect the wiring and test compressor winding resistance, which should measure approximately 6 to 7 ohms on a healthy unit.
Can I fix the 4 Flashes error on my Thermador refrigerator myself?
The initial diagnostic steps, such as inspecting wiring connections and checking for obvious damage, are within reach for a knowledgeable DIYer with a multimeter. Testing compressor winding resistance requires basic electrical skills but is straightforward. However, replacing a compressor or inverter board involves working with refrigerant systems and high-voltage components, which should be handled by a certified appliance technician.
Is it safe to keep using my Thermador refrigerator when it shows 4 Flashes?
No, the refrigerator is not safe to rely on for food storage when this code is active. The 4 Flashes fault means the compressor has stopped running, so the unit is no longer maintaining proper cooling temperatures. Food spoilage is a concern, and you should transfer perishables to another refrigerator or cooler until the fault is resolved.
Will resetting my Thermador refrigerator clear the 4 Flashes error?
A power reset may temporarily clear the fault and allow the refrigerator to attempt to restart, but the code will return if the underlying problem is not fixed. Resetting does not repair failed compressor windings or a faulty inverter board. Repeated resets without addressing the root cause can potentially cause additional damage to the inverter board or compressor.
How much does it cost to repair a Thermador refrigerator with the 4 Flashes error?
Repair costs vary significantly depending on the failed component. An inverter board replacement typically ranges from a few hundred dollars to over five hundred dollars including parts and labor. A compressor replacement is more expensive, often ranging from six hundred to over a thousand dollars depending on labor rates and part availability. Getting a diagnostic assessment from a certified technician first is the best way to understand the full scope of the repair before committing to costs.

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