LG dryer — Error Code D90
The exhaust duct is 90% blocked, severely restricting airflow and heat dissipation.
What it means
The D90 error code is triggered by LG's Flow Sense diagnostic system, indicating that the dryer's exhaust airflow is restricted by approximately 90%. The main control board calculates this restriction by monitoring the operating temperatures via the NTC thermistor. When airflow is choked, heat cannot escape the drum, causing the temperature to spike faster than the algorithm's baseline for normal operation. This is primarily a safety mechanism to prevent thermal fuse failure, heating element burnout, or a potential lint fire. While usually an external venting issue, a failing thermistor, a stripped blower wheel, or a weak blower motor can falsely trigger the D90 code by mimicking the thermal profile of a blocked vent.
Likely Causes
- 1 Clogged House Exhaust VentHeavy lint buildup in the wall or roof ducting is the most common cause, physically blocking exhaust air.
- 2 Crushed Transition DuctThe foil or semi-rigid hose behind the dryer is pinched or crushed against the wall, restricting airflow.
- 3 Internal Blower or Duct BlockageLint bypassing the filter can pack into the internal blower housing or blower wheel fins, reducing CFM output.
- 4 Faulty NTC ThermistorThe temperature sensor drifts out of specification, reporting false rapid temperature rises to the control board.
How to clear / reset
To clear the D90 code, you must resolve the airflow restriction. Start by removing and cleaning the lint filter. Disconnect the transition duct from the back of the dryer and inspect it for crushes or heavy lint. Next, clean your home's wall exhaust vent using a brush kit or vacuum. Once the venting is clear, perform a hard reset by unplugging the dryer for 5 minutes. Reconnect power and run a normal heated cycle. The Flow Sense system will recalibrate; if airflow is sufficient, the code will clear automatically.
Common replacement parts
When to call a pro
Call a professional if you have thoroughly cleaned the lint filter, transition hose, and wall vent, but the D90 code persists. This points to an internal hardware failure, such as a drifting NTC thermistor, a failing blower motor, or a malfunctioning main control board. Deep internal lint blockages also require complete drum removal to access the blower housing safely. Axis Appliance Repair offers a $90 diagnostic (waived if you proceed with the repair) and backs all work with a 1-year parts and labor warranty.
FAQs
How much does it cost to fix a D90 code?
If it is a clogged house vent, professional vent cleaning runs $100-$200. If an internal part like a thermistor or blower wheel has failed, appliance repair typically costs $150-$300 including parts and labor.
Can I bypass the D90 code and keep running the dryer?
No. The D90 code will stop the cycle to prevent overheating. Continuing to force the dryer to run with a 90% restriction risks blowing the thermal fuse, burning out the heating element, or starting a fire.
Will the D90 code clear itself?
It will only clear after the airflow restriction is removed and the dryer's Flow Sense system registers normal temperature gradients during a new cycle.
How long does it take to fix?
Clearing a basic vent clog takes 30-60 minutes. Replacing an internal thermistor or blower motor takes a technician about 45-90 minutes.
Does a D90 code mean my dryer is broken?
Not necessarily. In 90% of cases, the dryer is functioning exactly as designed by shutting down to protect itself from a dangerously clogged house vent.
Need help with D90?
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