Trane dehumidifier Model 5122 Not Working? Try This [2026]

Quick Fix Summary

Most Trane dehumidifier Model 5122 problems trace back to airflow restrictions, incorrect settings, or a mis-seated bucket or drain. Start by cleaning the air filter and coils, confirming the bucket or drain hose is correctly installed and clear, and setting the humidity to 45-50% with Fan on High. A simple power reset (unplug 5 minutes) often clears sensor hiccups and error indicators.

Step-by-Step Troubleshooting

Safety and preparation

Unplug the dehumidifier before cleaning or opening panels. Allow at least 5 minutes for internal pressures to equalize before restarting. Gather a soft brush, vacuum with a brush attachment, mild dish soap, white vinegar, a level, a flashlight, paper towels, and an external hygrometer to verify room humidity. If you plan to use the gravity drain, have a 3/4 in garden hose ready.

Typical specs and common symptoms

Check the rating label on your Trane dehumidifier Model 5122 for exact specifications. Common values for similar residential units include:

• Capacity: typically 50-70 pints/day at 80 F, 60% RH.
• Electrical: 115 V, 60 Hz with running current around 4-7 A (approximately 500-800 W).
• Operating range: roughly 41-95 F; performance falls off near the low end.
• Airflow: about 150-250 CFM; clear intake and exhaust are essential.
• Reservoir: about 1.6-2.0 gallons with an auto shutoff float switch.
• Refrigerant: many units use R410A; verify refrigerant type and factory charge on the label.

Common symptoms include: runs but collects little water, bucket full light stuck on, leaks when using a hose, frost or ice on coils, fan not spinning, or error indicators such as E1/E2 (sensor fault) and P1 (defrost mode).

1. Verify power and room conditions

   Confirm the outlet works by testing with a lamp or phone charger. Avoid extension cords and power strips that can cause voltage drop. Plug the unit directly into a grounded 3-prong outlet. Make sure the room is within 41-95 F. Close windows and doors and set a realistic target of 45-50% RH. If the unit recently shut off, wait 5-10 minutes before restarting to protect the compressor.

2. Reset controls and clean the air filter

   Unplug for 5 minutes to reset the control board. Remove the air filter from the intake grille, vacuum dust from both sides, then wash with mild soap and warm water. Rinse well and let it dry completely before reinstalling. Do not operate without the filter. Wipe intake and exhaust louvers with a soft brush to restore airflow.

3. Check the bucket and float switch alignment

   Empty the water bucket and reseat it firmly so alignment tabs engage. Inspect the float mechanism for slime or debris that might hold it in the raised position. Rinse the bucket with a 1:1 vinegar-water mix to remove biofilm. With power unplugged, gently press the bucket switch tab; you should feel a positive click. If the bucket full light remains on after reseating, the switch may be sticky or misaligned and might require replacement.

4. Set up or service the gravity drain

   If using continuous drainage, remove the internal bucket stopper or cap per the manual, then attach a standard 3/4 in garden hose to the drain port (many units use this thread; verify yours). Route the hose downward with a steady slope (about 1 in drop per 4 ft) to a floor drain. Avoid kinks, loops, or running the hose uphill. Flush the hose to clear residue, then test by slowly pouring 1-2 cups of water into the bucket area to confirm free flow. A clogged check valve or hose is a frequent cause of leaks.

5. Restore airflow and clear frost

   Place the dehumidifier at least 12 in from walls or furniture. Inspect the evaporator coil (cold coil behind the filter) and the condenser coil (warm coil near the exhaust) for lint and dust. If frosted, power off and let it defrost completely for 30-60 minutes. Clean fins with a soft brush, moving in the direction of the fins to avoid bending. A no-rinse coil cleaner can help, but keep liquids away from electronics. If frost quickly returns in a room above 50 F, suspect weak airflow (dirty filter, obstructed grille, failing fan) or a sensor issue.

6. Confirm settings, modes, and timers

   Set the mode to Continuous or set the humidity to 45% and Fan to High for initial drying. Disable any 24-hour timers or delayed start. Some models have a child lock; ensure it is off before changing settings. Compare the unit display with an external hygrometer; if there is more than a 5% difference after stabilization, the humidity sensor may need calibration or replacement.

7. Evaluate room moisture load

   Slow drying can stem from high moisture sources: damp foundations, unsealed crawlspace vents, laundry drying indoors, or unvented showers. Seal obvious air leaks and close exterior doors and windows. Run the unit continuously for 24-48 hours and monitor the bucket or drain output. If the space is large or extremely damp, the 5122 may need more runtime, a higher capacity unit, or multiple units working together.

8. Address error codes and short cycling

   P1 or defrost indication means the coil is too cold; allow defrost to complete and warm the room if possible. Generic E1/E2 codes often point to sensor faults or control issues. A full power reset (unplug 5-10 minutes) may clear temporary faults. Persistent sensor errors generally require replacing the thermistor or humidity sensor assembly. Short on-off cycles can be caused by a timer, an overly high setpoint, or poor airflow.

9. Resolve noise, vibration, and odors

   Use a level to ensure the cabinet is flat front-to-back and side-to-side. Isolate the feet with rubber pads if the floor is uneven. A rattling panel can be silenced by tightening accessible screws. Musty odors indicate biological growth; clean the bucket, drain tray, and hose with a 1:1 vinegar solution, then air-dry thoroughly. Avoid bleach near coils or metals to prevent corrosion.

10. Know when to call a technician

    If the fan does not spin freely, the motor or capacitor may be failing. A loud hum followed by a click suggests the compressor is not starting, often due to a weak run capacitor or overload. Oil stains on tubing or an uneven frost line can indicate a refrigerant leak. These conditions require professional service. Do not bypass safety switches or attempt sealed-system work without proper credentials.

Replacement Parts

Here are common parts for the Trane dehumidifier Model 5122. Verify compatibility by matching model and serial numbers and cross-checking part labels before purchase. You can browse options here: Replacement parts for Trane 5122.

• Air filter screen (intake filter)
• Bucket float switch or bucket full microswitch
• Drain hose and adapter kit (3/4 in garden-hose-thread, if applicable)
• Evaporator thermistor / defrost sensor
• Humidity sensor module (RH sensor) and control board
• Fan motor and fan blade; fan run capacitor if used
• Compressor run capacitor and overload relay (match the microfarad rating printed on the part)
• Water bucket assembly, gaskets, and drain check valve
• Caster wheels and cabinet screws

Tip: Keep your old part to compare connectors and ratings. When possible, use the exact part number from the label on the failed component to avoid returns. After installing a new part, perform a full power reset and recheck for proper drainage, airflow, and frost-free operation.