How to Fix Not drying — condenser pump clog on Bosch WTW87NH1UC (Condenser Heat Pump)

Not drying — condenser pump clog

This step-by-step repair guide walks you through fixing not drying — condenser pump clog on your Bosch WTW87NH1UC (Condenser Heat Pump). With the right tools and parts, most homeowners can complete this repair in 1–2 hours and avoid a costly service call.

Part of our Top 20 Dryer Models & Common Repair Issues Guide. Browse all dryer repair guides for related models and issues.

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Common Symptoms & Causes

The following symptoms point to a condenser pump clog on your Bosch WTW87NH1UC heat pump dryer.

Clothes come out damp or completely wet after a full drying cycle
The dryer displays error code E:02 or a condensation drawer warning
The condensate drawer remains empty even after multiple cycles
The drum runs and heats briefly, then the cycle extends unusually long without finishing

These issues are typically caused by lint, debris, or mineral buildup blocking the condenser pump, preventing it from evacuating collected moisture and disrupting the heat exchange cycle.

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Safety First

Unplug the dryer from the power outlet before starting any repair — never work on a live appliance.
Wear work gloves when handling metal brackets, sheet metal edges, or sharp components.
Take photos with your phone before disconnecting any wiring harnesses or connectors.
Work in a well-lit area with enough floor space to lay removed panels flat.

Tools & Parts Needed

Essential Tools

Phillips #2 screwdriver
¼” nut driver
Putty knife
Multimeter
Work gloves

Replacement Parts

Step-by-Step Repair Instructions

Step 1

Unplug the dryer before servicing, then open the condenser access panel on the lower-left front (it swings outward) and pull the lint filter from its slot. Rinse the filter under warm running water and let it dry completely before reinstalling — a clogged lint filter is the single most common cause of poor drying on heat pump models because it starves the condenser of airflow. Pro tip: keep a second clean filter on hand so you can swap immediately and run the dryer without waiting for the wet filter to dry.

Step 2

Slide out the base condensate tray from the lower-right area behind the access panel, empty any standing water, and wash the tray with warm soapy water. This tray collects the moisture extracted from your laundry, and an overfull or blocked tray can trigger the dryer’s flood-protection sensor and halt the drying cycle prematurely. Make sure the tray seats fully when reinstalled — a partially seated tray can cause the same sensor fault.

Step 3

With the tray removed, inspect the condenser fin block visible inside the lower chamber for lint buildup between the fins. Even a thin layer of lint across the fins dramatically cuts heat exchange efficiency, causing the dryer to run for hours without properly drying clothes. Use a soft brush to loosen debris, then vacuum it away — never use high-pressure air, which can bend the delicate aluminum fins.

Step 4

Bosch heat pump dryers work by recirculating warm air through a closed loop rather than exhausting it, which means all moisture and lint stays inside the machine and accumulates on the condenser filter. Unlike vented dryers that can tolerate occasional missed filter cleaning, heat pump models will noticeably underperform after just a few cycles with a dirty filter. Bosch recommends cleaning the condenser filter every 5 cycles as a hard minimum, not a suggestion.

Step 5

To test whether the condensate pump is the root cause, reinstall the condenser filter, remove the tray, plug the dryer in, and run a normal cycle while watching the pump outlet for water flow. If the pump is working correctly you will see water actively draining during the cycle; if there is no flow despite the tray area being wet, the pump motor has likely failed. Access the pump motor from the rear of the machine by removing 2 screws and disconnecting the wiring harness, then test for continuity with a multimeter before ordering a replacement. Safety note: unplug the dryer again before opening the rear panel.

Step 6

Reinstall the clean lint filter and condensate tray securely, then run a full normal cycle with a medium-sized load and note the total drying time. On a fully serviced Bosch WTW87NH1UC, a medium load should complete in 150–180 minutes — if the cycle runs significantly longer, the condenser filter is still partially blocked or the condenser fins need a more thorough cleaning. Repeat the filter inspection before running another load.

Where to Buy Replacement Parts

Find genuine OEM and aftermarket replacement parts for your Bosch WTW87NH1UC (Condenser Heat Pump) on Amazon:

When to Call a Professional

If the issue persists after completing all steps above, the problem may involve the sealed refrigerant system, a failed main control board, or wiring that requires specialized diagnostic equipment. Contact a licensed appliance technician — attempting sealed-system repairs without EPA 608 certification is illegal and unsafe.

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How Much Does This Repair Cost?

DIY parts for a condenser pump clog repair on the Bosch WTW87NH1UC typically run $15–$60, covering a replacement drain pump or cleaning supplies. A professional service call for the same issue generally costs $150–$300 in parts and labor. Tackling this repair yourself can save you $100–$250 or more.

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Frequently Asked Questions

How do I know if my Bosch WTW87NH1UC has a condenser pump clog and not another drying issue?

If your drum spins and heat generates but clothes remain wet, a blocked condenser pump is the most likely cause. You may also notice water pooling inside the drum or an error code on the display.

Can I clean the condenser pump myself without a technician?

Yes, most homeowners can clear a condenser pump clog by accessing the pump filter behind the front lower panel. Always unplug the dryer before starting any cleaning or inspection.

How often should I clean the condenser pump on my Bosch heat pump dryer?

Bosch recommends cleaning the condenser and pump filter every few months depending on usage frequency. Regular maintenance prevents clogs and keeps drying performance at its best.

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