Viking Oven: Cooling Fan Runs Constantly - Troubleshootin... | appliancefaults.com

Technical Background:

The Viking oven's Main Control Unit (MCU) monitors the oven temperature sensor and controls the cooling fan relay. When the oven reaches a certain temperature threshold after cooking, the MCU signals the relay to engage the cooling fan. The fan continues to run until the temperature drops to a safe level. The MCU relies on accurate sensor readings and a properly functioning relay to manage this process. Voltage paths from the sensor through the MCU determine fan runtime.

Symptoms:

The Viking oven cooling fan continues to run for an extended period (hours) after the oven has been turned off and cooled down. This is unusual and can be noisy and a potential waste of energy.

Possible Causes:

Faulty oven temperature sensor: An inaccurate reading can cause the MCU to believe the oven is still hot.
Defective cooling fan relay on the control board: A stuck or shorted relay will keep the fan running.
Short circuit in the fan motor wiring: This could provide power to the fan even when it's not supposed to be running.
Issues with the Main Control Unit (MCU) logic: The MCU may be misinterpreting data or sending incorrect signals.
Oven door switch malfunction: If the switch indicates the door is open, it might affect cooling fan operation.

Solution:

1

Disconnect power to the Viking oven at the breaker panel.
2

Locate the oven temperature sensor, usually at the top of the oven cavity. Using a multimeter, check its resistance at room temperature (approx. 75°F). Consult the service manual for the correct resistance value. Replace if out of range.
3

Access the main control board, usually located behind the control panel. Inspect the cooling fan relay. Test continuity across the relay coil using a multimeter. A reading of infinite resistance suggests an open coil. Look for signs of damage (burnt components, bulging capacitors). Replace the control board if the relay is defective.
4

Check the wiring harness to the cooling fan motor for shorts or breaks using a multimeter set to continuity. Repair or replace as needed. Also, verify you have 120V AC at the fan motor when it is running continuously.
5

Verify the oven door switch is functioning correctly. Use a multimeter to check for continuity when the door is open and closed. The switch should be normally open (no continuity) when the door is open and closed when the door is closed.
6

Reconnect power to the oven and monitor its operation after a test bake. If the problem persists after replacing the sensor or control board, the main control unit (MCU) may be faulty and require replacement by a qualified technician.

Safety Warning:

Always disconnect power to the oven at the breaker panel before performing any repairs. Verify the power is off with a non-contact voltage tester. Use Lock-Out/Tag-Out (LOTO) procedures to prevent accidental re-energizing of the circuit. The oven contains high voltage components that can cause serious injury or death.

Prevention:

Regularly clean the oven cavity to prevent grease buildup on the temperature sensor. Periodically inspect the cooling fan for proper operation and listen for unusual noises. Avoid slamming the oven door, which can damage the door switch.

Expert Tip:

Some Viking ovens have a service mode that allows you to test individual components, including the cooling fan relay. Consult the service manual for the specific sequence to enter service mode.

Frequently Asked Questions

•What is the typical resistance range for a Viking oven temperature sensor at room temperature?

The typical resistance range varies depending on the specific model, but it's usually between 1000 and 1200 ohms at 75°F. Always consult the service manual for your specific model.

•How can I identify the cooling fan relay on the main control board?

The cooling fan relay is typically labeled on the board or in the wiring diagram. It's usually a small, cube-shaped component with several terminals. Trace the wires from the cooling fan motor back to the relay.

•If the MCU is faulty, can it be repaired, or does it need to be replaced?

While some electronic components on the MCU can be repaired by qualified technicians specializing in circuit board repair, replacement of the entire MCU is often the more reliable and cost-effective solution. Viking doesn't officially support repair on that level.

Viking Oven: Cooling Fan Runs Constantly - Troubleshooting Guide

Technical Background:

Symptoms:

Possible Causes:

Solution:

Safety Warning:

Prevention:

Expert Tip:

Frequently Asked Questions

•What is the typical resistance range for a Viking oven temperature sensor at room temperature?

•How can I identify the cooling fan relay on the main control board?

•If the MCU is faulty, can it be repaired, or does it need to be replaced?

Related questions

Technical Background:

Symptoms:

Possible Causes:

Solution:

Safety Warning:

Prevention:

Expert Tip: