Honeywell 9934 Dehumidifier Not Working? Try This [2026]

Quick Fix Summary

Most Honeywell dehumidifier Model 9934 issues trace back to a dirty air filter, an improperly seated bucket or float switch, a blocked drain path, or settings that prevent the compressor from engaging. Start by cleaning the filter, confirming the room humidity is set below current humidity, seating the bucket firmly, and power-cycling the unit for 5 minutes to reset controls.

If the fan runs but no moisture is collected, ensure the space is within typical operating temperature and that coils are not frozen. Many units will auto-defrost and pause drying if the room is too cool.

Step-by-Step Troubleshooting

Safety and tools

Unplug before opening panels. Avoid working on the sealed refrigeration system. Helpful tools: flashlight, soft brush, vacuum with brush attachment, small level, thermometer/hygrometer, multimeter (for continuity and basic sensor checks), and a small bucket or towel.

Typical specs and operating limits (verify on your rating label)

• Power: 115 V, 60 Hz (typical for this class). Rated amperage is printed on the unit label.
• Moisture removal capacity: often 30-50 pints/day depending on ambient conditions. Actual capacity depends on room temperature and humidity.
• Operating temperature sweet spot: typically basements or spaces around basement comfort levels; many compressor dehumidifiers work best above about basement comfort temps and may reduce performance below about basement comfort temps. Check your label and manual.
• Refrigerant type: commonly R410A on modern units; confirm on the data plate.
• Drain options: removable bucket and optional gravity hose connection; ensure hose has continuous downward slope.

If your model plate lists different numbers, follow the label and manual over the ranges above. The data plate is usually on the cabinet side or rear.

1. Confirm power, placement, and settings

1. Outlet and voltage: Plug the Honeywell dehumidifier Model 9934 directly into a wall outlet (avoid long extension cords). Verify the outlet is live with another appliance. Reset GFCI if tripped.
2. Wait after moving: If the unit was transported or tipped, let it sit upright for 30 minutes before powering on so refrigerant can settle.
3. Room conditions: Use a thermometer/hygrometer to check actual humidity and temperature. Set the target humidity 5-10% lower than current humidity. If the room is very cool, performance will drop and coils may frost.
4. Mode and timer: Make sure no delayed start or timer is active. Try Continuous mode to force operation during testing.

2. Airflow and filter maintenance

1. Clean the filter: Remove and rinse the filter with mild soap and water; let it dry fully. A clogged filter greatly reduces airflow, causing poor drying and possible coil icing.
2. Check intake and exhaust: Keep at least 12-18 inches of clearance around grilles. Vacuum dust from louvers and gently brush coil fins from the intake side. Do not bend fins; use a fin comb if needed.
3. Fan test: Power on. If the fan does not run or sounds weak, the motor or capacitor could be at fault. Restricted airflow can also prevent the compressor from engaging.

3. Bucket, float switch, and drain path

1. Seat the bucket: Remove and firmly reseat the bucket. Ensure the float moves freely and the bucket lip fully depresses the safety switch. A misaligned bucket keeps the unit off.
2. Continuous drain check: If using a hose, remove it and test with the bucket only. Then reconnect a 1/2 in ID hose (or the size specified by your unit), ensuring a straight, downward slope to a drain. No kinks or uphills.
3. Leak and overflow: Inspect the internal drain spout into the bucket for clogs. Flush gently with warm water. Clear biofilm from the hose with a flexible brush. Place the unit level; use a small level to verify front-to-back and side-to-side alignment.

4. Compressor engagement and cooling check

1. Listen and feel: After the fan starts, the compressor should engage within a few minutes. You may hear a soft hum and feel warm air from the exhaust. The evaporator should get cool and the condenser warm.
2. Defrost behavior: If coils frost over, the unit may cycle into defrost. Turn the unit off and let ice melt. Improve airflow and raise room temperature. Restart once clear.
3. If fan runs but no cooling: This could indicate a faulty start capacitor, control board, or compressor. Do not open the sealed system. Proceed to electrical and sensor checks or call a pro.

5. Electrical basics and sensor checks (advanced users)

1. Capacitor: Unplug, discharge the capacitor safely, and compare microfarad reading to the value printed on its label using an appropriate meter. A failed capacitor can prevent the compressor or fan from starting. Replace if out of tolerance.
2. Bucket switch continuity: With the unit unplugged, test the bucket/float switch. It should read closed (continuity) when the bucket is properly seated and open when lifted. Replace if intermittent.
3. Humidity sensor: Many dehumidifiers use an RH sensor that changes resistance with humidity. If the display shows unrealistic readings or the unit never starts despite high humidity, inspect the sensor harness for damage and reseat connectors.
4. Defrost/coil sensor: Many models use a 10k NTC thermistor; resistance typically decreases as the sensor warms and increases when cooled. If the unit stays stuck in defrost or errors, check for reasonable resistance change when you gently warm/cool the sensor. Always confirm the correct spec for your exact board.

6. Control panel and error codes

1. Power reset: Unplug for 5 minutes, then plug back in to clear transient faults.
2. Keypad lock or non-responsive buttons: Some panels support a child lock. Check for a lock icon and hold the appropriate key combination (see manual) to toggle.
3. Error codes: Common codes may indicate sensor faults or bucket/float issues. Reseat connectors to the main board and sensor leads. If codes persist, the sensor or control board may need replacement.

7. Performance optimization

1. Seal the space: Close windows and doors. Dehumidifiers are most effective in enclosed areas.
2. Air circulation: Position the unit centrally with clear intake and exhaust. Run a circulating fan in large rooms to help moisture reach the intake.
3. Maintenance interval: Clean the filter every 2-4 weeks in dusty spaces. Inspect the drain path monthly to prevent algae buildup.

8. When to call a professional

If the compressor hums and trips, coils never get cool despite good airflow, or you see oily residue on tubing (possible refrigerant leak), contact a qualified HVAC technician. Refrigerant handling and sealed-system repairs require certification.

Common issues on Honeywell dehumidifier Model 9934

• No collection but fan running: Settings too high, room too cool, dirty filter, failed capacitor, or refrigerant issue.
• Unit shuts off quickly: Bucket not seated, float switch sticking, or sensor misreadings.
• Water on floor: Hose routing uphill, blocked internal spout, or unit not level.
• Excessive frost: Low room temperature or restricted airflow.
• Rattling noise: Loose bucket, vibration against a wall, or fan balance issue.

Replacement Parts

Many issues can be resolved with routine maintenance parts. For the Honeywell dehumidifier Model 9934, verify part numbers against your model label and service manual before ordering. Common replacements include:

• Air filter: Restores airflow and protects coils. Cleanable, but replace if torn or warped.
• Bucket float switch or bucket assembly: Fixes false bucket-full shutoff and seating issues.
• Drain hose and adapter kit: Ensures reliable continuous drainage with a proper seal and slope.
• Fan motor and fan blade: Resolves weak airflow, humming, or seized bearings.
• Compressor or fan start/run capacitor: Corrects non-starting motors when testing shows out-of-spec capacitance.
• Humidity (RH) sensor and coil/defrost sensor: Restores accurate readings and prevents improper defrost cycling.
• Main control board (PCB) and relay kit: Addresses persistent error codes, non-responsive controls, and relay failures.

Shop compatible parts here: https://www.amazon.com/s?k=Honeywell+dehumidifier+Model+9934&tag=manuallogic-20. Cross-check dimensions, connectors, and ratings printed on your current components to ensure a proper match. If in doubt, contact Honeywell support with your full model and serial number for confirmation.

With the steps above, most Honeywell dehumidifier Model 9934 problems can be diagnosed and fixed at home. Start with airflow and bucket alignment, verify room conditions, and only then move to electrical checks. Consistent filter care and a clear drain path go a long way toward keeping your 9934 running efficiently and safely.