Lg Microwave: vent fan running during operation

Professional Repair Guide

What is this symptom?

Is your LG microwave's vent fan running during cooking cycles or continuing after? This could be due to normal cooling functions, high internal temperatures, or potential faults like a faulty temperature sensor. Understanding these causes can help you address the issue effectively.

Urgency: Low

Important Tips for Lg Models

  • LG’s official support documentation does not detail ventilation fan run durations; consult model manual for expected behavior

Possible Causes

Normal cooling/ventilation function during and after cooking

How to Identify: Fan runs during cook cycle and may continue briefly after cooking, especially during long or high‑power use

Part: Microwave cooling/ventilation fan system

High internal temperature due to prolonged or high‑power cooking

How to Identify: Fan continues running longer when appliance was heavily used, cooking times were long, or kitchen ambient temperature is high; no error codes present

Part: Internal temperature sensors/thermal management

Faulty temperature sensor/thermostat

How to Identify: Fan runs for excessively long periods well beyond expected cool‑down time; may coincide with other faults; resetting power doesn’t stop fan

Part: Thermostat/temperature sensor

Control board or relay malfunction

How to Identify: Fan runs continuously unrelated to temperature or cooking cycles; other functions may be erratic

Part: Main control board/fan relay

Clogged vents/filters increasing workload

How to Identify: Visible buildup on vent grilles/filters; fan runs longer to compensate for restricted airflow

Part: Air vents, grease filters

DIY Solutions

Allow normal cool‑down time

Easy 5–15 minutes
  1. Finish cooking and allow the fan to run its built‑in cool‑down cycle
  2. Wait a few minutes after cooking to see if fan shuts off on its own
⚠️ Safety First: No internal access or electrical work required

Clean exterior vents and grease filters

Moderate 10–20 minutes
Tools Needed: Soft cloth, Mild cleaner
  1. Unplug microwave
  2. Remove and clean vent grilles/filters according to manual
  3. Ensure vents are unobstructed before use
⚠️ Safety First: Ensure unit is unplugged before cleaning vents

Reset microwave power

Easy 5 minutes
  1. Unplug microwave from power for ~5 minutes
  2. Plug back in to reset control board
  3. Test whether fan operation returns to normal
⚠️ Safety First: Follow manual reset guidance

Professional Repairs

Replace temperature sensor/thermostat

Estimated Cost: $60 – $150

Control board or fan relay replacement

Estimated Cost: $100 – $300

Service/clean internal ventilation system

Estimated Cost: $80 – $200

When to Call a Professional

Fan runs continuously for 20+ minutes after cooking
Fan runs non‑stop regardless of usage
Other functions (control panel, error codes) are malfunctioning

Preventive Maintenance

  • Regularly clean vent grilles/filters: Restricted airflow and extended fan running
    Frequency: monthly or as needed
  • Avoid prolonged continuous high‑power cooking: Excessive internal heating triggering extended fan cycles
    Frequency: as used

Frequently Asked Questions

Why is my LG Microwave vent fan running during operation?
The vent fan runs due to normal cooling, high temperatures, or potential issues with the temperature sensor or control board.
How do I fix LG Microwave vent fan running during operation myself?
Try allowing the fan to cool down, clean vents and filters, or reset the microwave by unplugging it for 5 minutes.
How much does it cost to fix vent fan running during operation?
Professional repair costs range from $60 to $300, depending on whether the thermostat or control board needs replacement.
When should I call a technician for vent fan running during operation?
Consider calling a technician if cleaning and resetting don't resolve the issue or if the fan continues running excessively.

References & Sources

Community Analytical Insights

Analysis based on real user discussions from appliance repair communities

Can I Fix This Myself?

60%
DIY Success Rate Difficulty: Either

Common Issues Reported by Users

  • The vent fan is designed to run during cooking to expel heat and steam, which is a normal function.
  • The microwave's control board may be malfunctioning, causing the fan to run continuously.
  • Improper installation of the vent fan exhaust, leading to incorrect airflow and continuous operation.

User Suggested Solutions

  1. Verify if the vent fan is operating normally by checking if it turns off after the cooking cycle. If it continues running, proceed to inspect the control board for faults.

  2. Inspect the installation of the vent fan exhaust. Ensure it is properly seated in the duct and that there are no obstructions.

  3. If the control board is suspected to be faulty, consider replacing it. This may require professional assistance to ensure proper installation.

Analysis based on 1 community discussions
View Sources

Data compiled from real discussions on r/appliancerepair and r/Appliances:

  1. LG Microwave vent fan runs when microwave is cooking

Community Discussions

vent fan runs when microwave is cooking

Installation error; vent fan exhaust not properly seated in the duct.

DIY View on Reddit →

Source: Reddit r/appliancerepair

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