LG Dryer d90 — Exhaust Duct 90% Blocked

What does LG d90 mean?

Severe duct blockage — 90% restriction detected by FlowSense. The dryer will continue to run but at risk of overheating, tripping the thermal fuse, and potentially causing a fire.

What causes LG d90?

• Heavy lint buildup over years without cleaning
• Duct elbows packed with accumulated lint
• Damaged duct allowing lint to escape and pack in the wall cavity

How a technician tells the causes apart

• Pull the lint trap and hold it up to a light: a screen that looks solid gray instead of see-through mesh has been trapping lint fine while the duct behind it packed up silently over months or years.
• Disconnect the exhaust duct where it meets the back of the dryer and feel for airflow with your hand while a helper runs the dryer briefly on Air Fluff — weak or no airflow at the first foot of duct confirms restriction close to the machine.
• Work your way along each duct section and elbow, checking for a soft, felt-like plug of lint packed against the inside wall, especially at any 90-degree turns — elbows clog first because lint loses velocity going around the bend.
• If any duct run is flexible foil or plastic hose rather than rigid metal, inspect it for sagging or crushed sections: flexible duct collapses under its own weight and creates a choke point lint collects against.
• Follow the full duct path out to the exterior vent cap and check that the cap's flap opens freely when you blow into the duct from the dryer end — a flap stuck shut from outside debris restricts airflow even after the inside is clean.
• Once every section is cleared, run a full cycle and recheck for the d90 code: if it returns immediately with a duct you know is clean, the FlowSense airflow sensor itself may be reading wrong and needs a technician's evaluation.

Duct clearing solves d90 in most cases, but a run that overheated badly enough to trip the thermal fuse also needs that fuse replaced before the dryer will start again — it's a one-time safety part, not something to bypass or jumper. The model and serial tag on LG dryers usually sits inside the door frame along the inner edge, most often near the right side of the opening; if it isn't there, check the label on the back panel near the power cord.

How to fix LG d90 yourself

1. 1 Stop the dryer immediately.
2. 2 Clean the lint trap.
3. 3 Inspect and clean the full duct run before restarting.