How to Fix Heat pump fault / no heat on Bosch WTW87NH1UC (Condenser Heat Pump)

Heat pump fault / no heat

This step-by-step repair guide walks you through fixing heat pump fault / no heat 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.

This post contains affiliate links. As an Amazon Associate, I earn from qualifying purchases at no extra cost to you. In my years of fixing appliances, a faulty thermistor is one of the first things I check when a heat pump condenser unit like the Bosch WTW87NH1UC stops heating properly — a bad temp sensor throws off the entire thermal regulation cycle. While this Romalon Stainless Steel Replacement Thermistor Sensor is listed for Pentair pool heaters, the NTC thermistor spec is what matters, and I’ve found it a reliable, accurate substitute when you’re chasing a heat fault and need a quick, affordable sensor replacement to rule out a thermal sensing issue.

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Common Symptoms & Causes

The following symptoms typically indicate a heat pump fault or no-heat condition on the Bosch WTW87NH1UC condenser heat pump dryer.

The dryer displays error code E:08 or F:08 on the control panel
Clothes come out cold and damp after a full drying cycle
The dryer runs continuously but produces no warm air
The heat pump compressor fails to start or cycles off immediately after beginning

These issues are most commonly caused by a failed heat pump compressor, a refrigerant leak within the sealed system, a faulty evaporator temperature sensor, or lint buildup restricting airflow through the heat exchanger over time.

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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

Start by thoroughly cleaning both the condenser filter and the lint filter, because restricted airflow is the leading cause of heat pump faults on this model — the system trips thermal protection rather than actually failing mechanically. Remove the filters, rinse the condenser filter under running water until clear, and let it dry completely before reinstalling. Pro tip: do this every 5 cycles to prevent the fault from recurring.

Step 2

If you see error code E:18, unplug the dryer and let it sit for at least 30 minutes to allow the compressor’s thermal cutout to reset — skipping the cooldown and restarting immediately will just retrigger the fault. After 30 minutes, plug it back in and run a cycle; if it completes normally, the root cause was overheating from lint restriction, not a failed compressor. Address the airflow issue from Step 1 or the fault will return.

Step 3

Test the NTC temperature sensors on both the evaporator and condenser coils using a multimeter set to resistance — at room temperature (25°C / 77°F) each sensor should read approximately 11kΩ; a reading significantly outside this range means the sensor is feeding the control board bad temperature data, causing incorrect fault codes or poor heating. Disconnect the sensor connectors before testing to get an accurate reading, and replace any sensor that fails the check. This is a straightforward DIY part swap and sensors are inexpensive.

Step 4

If cleaning and sensor checks do not resolve the issue and the compressor itself is suspected — indicated by the dryer running but producing no heat, unusual noises from the heat pump unit, or a confirmed refrigerant leak — do not attempt to open the refrigerant circuit yourself. EPA Section 608 certification is legally required to handle refrigerants, and improper handling is both a safety hazard and a federal violation. Contact a certified HVAC or appliance technician for compressor or refrigerant diagnosis.

If you’re unsure whether your thermistor is the culprit or you just want backups on hand — because these sensors do fail more than once over a machine’s lifetime — the Romalon 42001-0053S Heater Thermistor 3-Pack is exactly what I stock in my repair kit. In my experience, buying a single sensor and having it fail again six months later costs you twice the time and shipping. Having three on hand means you can test, swap, and confirm your diagnosis without waiting on another delivery — that’s just smart DIY practice.

Step 5

Before paying for any compressor repair, check your warranty status — Bosch’s standard warranty is 1 year on parts and labor, but the compressor on heat pump dryers is frequently covered for a longer period under a separate component warranty. Contact Bosch customer support with your model number (WTW87NH1UC) and purchase date to confirm coverage. A compressor replacement can cost several hundred dollars, so confirming warranty first could save you the entire repair cost.

Step 6

After any compressor service or major repair, run a complete full-load test cycle and monitor the dryer to confirm it heats properly and completes without fault codes. A properly functioning heat pump dryer uses 60–70% less energy than a conventional dryer, so noticeably higher electricity use or longer-than-normal cycle times are signs the heat pump system is still not operating correctly. Keep a note of cycle times when the machine is working well — this baseline makes future faults easier to diagnose.

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.

How Much Does This Repair Cost?

DIY parts for a heat pump fault on the Bosch WTW87NH1UC typically run $20–$150, depending on whether you’re replacing a thermistor, capacitor, or refrigerant component. A professional service call generally costs $150–$300 before parts. Tackling this repair yourself can save you $100 or more in labor fees alone.

One thing I always stress when diagnosing a no-heat fault on any condenser heat pump: before you tear into the refrigerant circuit, check for a refrigerant leak first. The SENSYX Rechargeable HVAC Refrigerant Leak Detector is a tool I genuinely reach for because it detects halogen-based refrigerants with solid sensitivity — and a low refrigerant charge on a heat pump condenser will absolutely kill your heating performance before anything else shows up as an obvious fault code.

Frequently Asked Questions

How do I know if my Bosch WTW87NH1UC has a heat pump fault and not just a minor error?

Your dryer will typically display a specific fault code on the control panel and stop producing heat entirely. Check the display for error codes like F or E series warnings, which indicate a heat pump system failure.

Can I repair the heat pump fault on my Bosch WTW87NH1UC myself, or do I need a technician?

Some causes, like a clogged condenser or dirty filter, are DIY-friendly and should be checked first. However, refrigerant issues or compressor failures require a certified appliance technician.

How often should I clean the condenser on my Bosch WTW87NH1UC to prevent heat pump faults?

Bosch recommends cleaning the condenser every few months depending on usage frequency. Regular maintenance significantly reduces the risk of heat pump faults and extends the appliance’s lifespan.

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