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LG Dryer Error Code d90: What It Means and How to Fix It
Ninety percent is the second-worst score LG's Flow Sense system can give your vent, one step short of the d95 reading that means stop using the dryer altogether. The machine is not broken; it has measured the exhaust path through your house and found it nearly closed. Set aside an hour or two for a full vent clean, because at this level of blockage a wiped lint screen will not move the reading, and running load after load against a vent this tight is how dryers overheat.
What is happening inside the machine
Every dryer cycle is a controlled wind tunnel. The blower draws room air over the heater, through the tumbling clothes where it loads up with moisture, and out through the vent to the outside air. Flow Sense is LG's way of auditing that journey. Sensors judge how freely the exhaust is moving and the control converts the result into a blockage percentage, displayed as a code from the same family: d80 for a vent measuring about 80 percent blocked, d90 for about 90 percent, and d95 when the vent is effectively fully blocked.
The percentage describes your house, not your appliance. Between the drum and the daylight sit the lint screen, a short transition duct behind the machine, a duct run that may travel through walls, floors or a roof, and a hood on the outside wall. Lint escapes the screen a little at a time and settles wherever the air slows down: at elbows, at joints, in sags, and against the hood flap. Year by year the passage narrows until the blower is pushing against a wall of felted lint. At 90 percent blocked the dryer still runs, but it runs hot and long, drying suffers because the moist air has nowhere to go, and the lint packed inside a hot duct is precisely the fire risk these codes exist to prevent. Nothing in the measurement points at a failed part, which is why the remedy is cleaning rather than repair.
Finding the cause
Test the lint screen under a tap
Dryer sheets coat the screen mesh with an invisible residue that traps lint and slows air before it ever leaves the drum, and the screen can look spotless while coated. Hold it under a running tap. Water passing straight through clears the screen of suspicion. Water pooling on the mesh confirms the film, and it also tells you something useful: a household habit, sheet use, is feeding the larger build-up problem downstream.
Inspect the transition duct behind the dryer
Unplug the machine and pull it forward. The short duct between the dryer and the wall is the narrowest, most abused section of the path, and it flattens a little more every time the dryer is pushed back into its space. A crushed section here throttles the entire system at its starting point. Finding the duct flattened is good news in disguise: replace it with rigid or semi-rigid metal, kept short and straight, and a large share of the restriction may vanish before you touch the main run.
Brush the full duct run and judge what comes out
The main run through the house is where most of the blockage volume lives, especially where the duct turns or climbs. A rotary brush kit on a drill, worked from the dryer end and from the outside end on long runs, is both the test and the treatment. Heavy lint coming out of the middle sections confirms ordinary build-up as your cause. A brush that comes back surprisingly clean, on a dryer still reading d90, redirects you: the restriction is then likely a crushed section hidden in a wall, a run far longer than the installation allows, or a hood that is blocked at the exit.
Stand at the outside hood while the dryer runs
The last check needs the dryer running a heat cycle and you standing outside. The hood flap should stand open under a strong, steady stream of warm air. Lint mats and nest material often felt across this opening, invisible from indoors. A weak, lazy flow after a full clean tells you a section of the run is still obstructed or disconnected. A strong blast tells you the path is open and the next cycle should measure it that way.
What your findings mean
| What you find | What it means | What to do next |
|---|---|---|
| Water pools on the lint screen mesh | Softener film is coating the screen | Wash it with soap, warm water and a brush, dry fully, and retest |
| Transition duct crushed behind the dryer | The path is throttled at its narrowest point | Replace with rigid or semi-rigid metal duct, short and straight |
| Heavy lint brushed out of the mid-run | Ordinary duct build-up is the main restriction | Finish the clean from both ends and run a test load |
| Weak flow at the hood after cleaning | A section is still blocked, crushed or disconnected out of sight | Call a vent specialist to trace the run |
| The code steps up to d95 | The vent is effectively fully blocked | Stop using the dryer until the vent is cleared |
Fixing it
- Wash the lint screen (10 minutes). Soap, warm water and a soft brush, then rinse and let it dry completely. The tap test afterwards should show water passing freely.
- Replace a crushed transition duct (20 to 30 minutes). With the dryer unplugged and pulled forward, fit rigid or semi-rigid metal duct in place of any foil or plastic hose, as straight as the space allows. Be gentle brushing near any remaining flexible sections so the brush does not tear them.
- Vacuum the dryer outlet (5 minutes). With the duct disconnected, clear the outlet and the first section of duct with a crevice tool.
- Brush the full run (30 to 60 minutes). Work the rotary brush through the whole duct from the dryer end, and from the hood end too on long runs, vacuuming the loosened lint as you go.
- Clear the outside hood (10 minutes). Remove lint mats and nest material, confirm the flap swings freely, and remove any mesh screen fitted over the outlet, since screens trap lint at the exit.
- Test with a real load (one cycle). Run a timed load of towels on a heat setting and check the hood mid-cycle for a strong flow. A healthy reading on the next Flow Sense check confirms the fix.
Reset and Clearing
Flow Sense codes do not clear with a button press or a power cycle, because they are measurements, not glitches. d90 clears when a later cycle measures a clear vent. That is by design: LG would rather nag you about a fire risk than let a reset hide it. If the code survives a genuinely thorough cleaning, the remaining suspects are a vent run that is too long for the installation, or a section crushed or disconnected inside a wall, and that is a job for a vent specialist.
What it costs
| Item | DIY cost | Part only | Fitted by a service |
|---|---|---|---|
| Full vent path clean | $20 to $40 for a brush kit | Brush kit $20 to $40 (estimate) | $100 to $200 for a professional vent cleaning (estimate) |
| Lint screen wash and hood clear | $0 | No part needed | Included in a cleaning visit |
All prices on this page are estimates based on typical US parts and service pricing. Your model, region and the actual failed part will move the real figure.
Repair or replace: d90 is never a reason to replace the dryer, because the blockage belongs to the house. The only scenario that calls for real money is a run that is too long, crushed inside the structure, or terminated in the wrong place, and in that case the spend goes on correcting the duct, after which the existing dryer will read a healthy vent again.
Mistakes that make it worse
Wiping the lint screen and calling it cleaned. The screen is the first few inches of the path and at d90 the blockage is measured across the whole route. Owners who stop at the screen watch the code return immediately and conclude the sensor is faulty.
Running the dryer unattended while the code is active. A vent blocked at 90 percent makes the machine run hot by design of the fault. Loads run overnight or while you are out remove your chance to react to the one symptom that matters, a burning smell.
Brushing aggressively through foil or flexible duct. A rotary brush can tear thin duct inside a wall, turning a blockage into a disconnected vent that fills the wall cavity with hot moist air. Work gently, or replace fragile sections with metal first.
Leaving a mesh screen over the outside hood. Screens fitted to keep birds out catch lint at the exit and rebuild the blockage from the far end. The flap hood on its own is the correct guard.
Stop and Call a Professional If
- The dryer shows d95, meaning the vent is effectively fully blocked: stop using it until the vent is cleared
- You smell burning, or find scorched lint anywhere in the duct or around the heater housing
- d90 returns within weeks of a thorough cleaning, suggesting the duct is crushed, disconnected inside a wall or ceiling, or terminated somewhere unsafe such as an attic
- The outside hood cannot be reached or the run goes through a roof you cannot safely access
Unplug the dryer before any work behind it or inside the duct connection. Never run a dryer with a known severe vent blockage, and never work on gas lines, sealed refrigerant systems or inside electrical panels. If anything in this guide conflicts with your model's manual or a safety warning on the machine, the manual and the warning win.
Samsung runs the same idea under a different name, the Vent Blockage test on our Samsung d80 page, and the cleaning routine is identical. Back to the full list: Dryer Error Codes
Frequently Asked Questions
What does d90 mean on an LG dryer?
d90 is an LG Flow Sense result: the dryer measured its exhaust vent at about 90 percent blocked. Airflow is so restricted that the dryer cannot dry efficiently, and the code is a warning to clean the entire vent path, not just the lint screen.
What is the difference between d80, d90 and d95 on LG Flow Sense?
They are steps on the same blockage scale: d80 means about 80 percent blocked, d90 about 90 percent, and d95 means the vent is effectively fully blocked. At d95, stop using the dryer until the vent is cleared, because the machine is pushing hot air into a dead end.
Why does d90 come back right after I clean the lint screen?
Because the screen is only the first few inches of the path. Flow Sense measures the whole route: the transition duct behind the dryer, the duct run through the house, and the outside hood. A crushed duct or a clogged run will still read d90 with a spotless screen.