LG Dryer Error d90: Flow Sense 90% Blocked

The Logic Verdict

The LG short shows the dryer powered up on a Normal cycle with the Energy Saver light glowing. While Flow Sense was flashing d90, the tech points out that Energy Saver intentionally suppresses the heater for the first 40–45 minutes. That delay tricks users into thinking the dryer has no heat or that the vent is still blocked. The moment he toggles Energy Saver off, the heater fires and the d90 warning clears. Use that quick panel check before tearing apart ductwork, then clear any real restrictions so Flow Sense stops seeing 90% back pressure.

What It Means

The d90 alert means LG’s Flow Sense system is measuring roughly 90% exhaust restriction. The control adds Energy Saver logic on top of that: when the feature is enabled, it delays full heat output, so the airflow sensors can’t see the temperature rise they expect and the d90 flag stays latched. If you turn Energy Saver off and the code persists, you truly have a venting problem that needs to be corrected before the dryer overheats and trips safety thermostats.

Common Causes

• Energy Saver left on. With the light on, the heater waits up to 45 minutes, so Flow Sense never sees enough airflow and calls d90.
• Lint-packed duct runs. Loose lint inside the wall or ceiling vent raises static pressure and trips Flow Sense.
• Crushed or extra-long transition hose. Foil hoses folded behind the cabinet or too many elbows choke the blower.
• Blocked termination. Bird guards, stuck louvers, or snow buildup outside the house keep air from escaping.

Step-by-Step Fix

1. Check the control panel first. Power on the dryer, select Normal, and confirm the Energy Saver indicator is off. Tap the button to disable it so the heater engages immediately.
2. Clean the lint filter and drum sensors. A plugged lint screen or waxy moisture sensor pads slow airflow and extend dry times even with clear vents.
3. Inspect the transition duct. Unplug the dryer, slide it out, and remove the 4-inch hose. Replace crushed foil with a short, smooth semi-rigid duct that keeps its shape when you push the dryer back.
4. Brush out the wall duct. Run a vent brush or rotary kit from the dryer side to the exterior cap, clearing every elbow until the brush spins freely. Vacuum the termination hood and ensure the flapper swings easily.
5. Reassemble and test Flow Sense. Reconnect the duct, restore power, and run a timed dry with a load of damp towels. The Flow Sense bars should disappear after a few minutes; if they don’t, repeat the vent inspection or look for hidden booster fans/extra-long runs that need professional cleaning.

Parts & Tools

• Gardus LintEater RLE202 rotary vent-cleaning kit (cleans long duct runs from inside)
• Deflecto semi-rigid transition duct with clamps (replaces crushed foil hoses)

Resources