i just emptied the dust cup but my shark still has terrible suction. it feels weak.

Diagnosis

The Shark Navigator Lift-Away NV352 utilizes a multi-stage filtration system that is highly prone to "invisible" clogging. While emptying the dust cup removes large debris, microscopic dust particles embed themselves into the pores of the foam and felt filters. When these pores are blocked, the motor continues to spin at full speed, but the airflow (CFM) drops significantly, resulting in the "weak suction" feeling where the vacuum fails to lift carpet fibers or pull debris from the floor. This issue is often compounded by a blockage in the intake pathways. Because the NV352 features a "Lift-Away" pod, there are multiple connection points where hair, coins, or clumps of pet fur can lodge. If the airflow is restricted at any point between the floor nozzle and the motor exhaust, the vacuum will lose its ability to create a vacuum seal, making it feel as though the motor is struggling or underperforming despite the dust cup being empty.

How to Fix It

To restore full suction, you must perform a deep clean of the filtration system and a clear-out of the air paths. Follow these exact steps:

1. Detach the Lift-Away Pod: Press the release button and lift the canister pod away from the main floor nozzle.
2. Access the Primary Filters: Press the release button on the dust cup to remove it. Locate the pre-motor foam filter and the felt filter located directly behind the dust cup area.
3. Wash the Filters: Remove both filters and rinse them under a faucet with lukewarm water. Do not use soap or detergents, as these can leave a residue that further restricts airflow. Continue rinsing until the water running through the foam is crystal clear.
4. Dry Properly: Gently squeeze the foam filter to remove excess water—do not wring or twist it, as this tears the cellular structure. Lay them flat on a towel in a well-ventilated area. They must air dry for a full 24 to 48 hours.
5. Clear the Hose: While the filters dry, disconnect the hose from the pod. Drop a heavy coin or a marble through the hose; if it doesn't fall through instantly, use a broom handle or a flexible plumbing snake to push the obstruction out.
6. Check the Brush Roll: Flip the vacuum over and check the brush roll for tangled hair or string. Use scissors to cut away debris that is choking the rotation of the brush, as a stalled brush roll prevents debris from being lifted into the suction stream.

If That Didn't Work

• Inspect the Post-Motor HEPA Filter: On the back of the NV352 pod, there is a plastic cover protecting the HEPA filter. Unscrew or snap open this cover. If the pleated white filter is grey or brown, it is saturated. Unlike the foam filters, the HEPA filter should not be washed; it must be tapped against a hard surface to knock out dust or replaced entirely with a new part.
• Check the Floor Nozzle Intake: Look at the gap between the brush roll and the plastic housing of the floor head. Large debris like pebbles or LEGOs often get stuck right at the entrance of the suction throat before they even reach the hose. Use a flashlight to ensure the path is completely clear.
• Verify the Hose Connection Seals: Inspect the rubber gaskets where the hose connects to the pod. If the rubber has perished or is pinched, air will leak into the system, causing a massive drop in suction pressure at the floor level.
• Test the "Lift-Away" Seal: Ensure the pod is clicked firmly back into the base. If the pod is not seated perfectly, the air bypasses the suction path, resulting in almost zero suction at the floor nozzle.

Heads Up

• The 24-Hour Rule: Never install damp filters. Even a slightly moist filter can allow moisture to be sucked into the motor housing, leading to permanent motor failure or a burnt-out circuit board.
• Avoid "Water-Only" Cleaning: Do not submerge the entire dust cup or the motor pod in water. Only the removable foam and felt filters are washable.
• Filter Replacement Cycle: While washable, the foam and felt filters lose their structural integrity over time. Replace them every 6-12 months depending on usage to maintain peak CFM.
• Hair Maintenance: Cut hair off the brush roll every two weeks. If hair wraps tightly around the axle, it creates friction that slows the motor and reduces the "flicking" action needed to push dirt into the suction stream.