Sub-Zero Refrigerator Error Code 12: Evaporator... | appliancefaults.com

Technical Background:

Error Code 12 on a Sub-Zero refrigerator indicates a fault in the evaporator thermistor circuit. The main control unit (MCU) monitors the resistance of the evaporator thermistor to determine the temperature of the evaporator coil. If the MCU detects an out-of-range resistance value, or an open/short circuit, it triggers Error Code 12. The thermistor provides a variable voltage signal back to the MCU. A break in the 5V circuit will also trigger the error.

Symptoms:

Homeowners often report that their Sub-Zero refrigerator isn't cooling properly, the freezer may be warmer than usual, or the unit displays 'Error Code 12' on the control panel. The ice maker may also stop working if the freezer temperature is affected.

Possible Causes:

Faulty evaporator thermistor.
Wiring harness issue between the thermistor and the main control board.
Loose connection at the thermistor or the control board.
Damaged main control board.
Ice buildup around the evaporator thermistor.
Improper thermistor placement.

Solution:

1

Disconnect power to the refrigerator at the breaker panel.
2

Locate the evaporator thermistor, typically behind the evaporator panel inside the freezer compartment. Use a 1/4-inch nut driver to remove the panel screws.
3

Inspect the wiring harness and connectors for any signs of damage, corrosion, or loose connections.
4

Using a digital multimeter, measure the resistance of the thermistor. Compare the reading to the thermistor's resistance chart at the current freezer temperature. An open or short circuit indicates a faulty thermistor.
5

If the wiring and thermistor check out, inspect the main control board. Look for any burnt components or signs of damage.
6

If the thermistor is faulty, replace it with a new, OEM-approved thermistor.
7

Reassemble the refrigerator and restore power. Monitor the refrigerator for proper operation and to ensure the Error Code clears.

Safety Warning:

Always disconnect power to the refrigerator at the breaker panel before performing any repairs. This appliance operates at 120V AC, which can cause serious injury or death. Follow Lock Out/Tag Out (LOTO) procedures.

Prevention:

Regularly defrost the freezer compartment to prevent ice buildup around the evaporator coil and thermistor. Inspect the wiring harness and connections periodically for any signs of damage or corrosion. Avoid overloading the refrigerator to maintain proper airflow and cooling efficiency.

Expert Tip:

Some Sub-Zero models allow you to enter a diagnostic mode by pressing a specific sequence of buttons on the control panel. Consult the service manual for the correct sequence for your model. This mode can provide more detailed information about the error and system performance.

Follow-up Questions:

Frequently Asked Questions

•What is the typical resistance range for the evaporator thermistor at 32 degrees Fahrenheit?

The resistance range for a typical Sub-Zero evaporator thermistor at 32 degrees Fahrenheit is approximately 6,000-8,000 ohms. Refer to the specific service manual for your model for exact values.

•How can I confirm that the wiring harness is not damaged without a multimeter?

Visually inspect the wiring harness for any obvious signs of damage, such as cuts, frayed wires, or corrosion. Gently tug on the wires to check for loose connections. However, a multimeter is the most reliable way to test continuity and identify internal wire breaks.

•Where can I find the evaporator thermistor resistance chart for my specific Sub-Zero model?

The evaporator thermistor resistance chart is typically located in the service manual for your specific Sub-Zero model. You may be able to find it online through Sub-Zero's website or appliance parts retailers. Some charts are inside the unit taped to the wiring diagram.

Sub-Zero Refrigerator Error Code 12: Evaporator Thermistor Troubleshooting Guide

Technical Background:

Symptoms:

Possible Causes:

Solution:

Safety Warning:

Prevention:

Expert Tip:

Frequently Asked Questions

•What is the typical resistance range for the evaporator thermistor at 32 degrees Fahrenheit?

•How can I confirm that the wiring harness is not damaged without a multimeter?

•Where can I find the evaporator thermistor resistance chart for my specific Sub-Zero model?

Related questions

Technical Background:

Symptoms:

Possible Causes:

Solution:

Safety Warning:

Prevention:

Expert Tip: