Bosch Dryer Error Codes: Full Guide for Heat Pump & Ventless Models

Bosch dryers are fundamentally different from most American brands. While traditional dryers blast hot air through clothes and vent moisture outside, Bosch heat pump dryers use a closed-loop refrigerant system that recycles air — no external vent required. This design is more energy-efficient (about 50% less electricity than conventional dryers) and gentler on fabrics, but it also means the error codes and troubleshooting are unique. This guide covers every Bosch dryer error code across the 500 Series (WTW87NH1UC), 800 Series (WTX87NH1UC), and compact condensation models (WTG86401UC) including Home Connect-enabled units.

How Bosch Dryer Error Codes Work

Bosch dryers monitor temperature, moisture levels, airflow, and the heat pump refrigerant circuit through multiple sensors. When a sensor detects a problem, the control board displays an E-code on the panel. Unlike conventional vented dryers with simple heating elements, Bosch heat pump dryers have a compressor, evaporator, and condenser — similar to an air conditioner running in reverse. This added complexity means some error codes are specific to the heat pump system.

Standard reset procedure:

1. Press Power to turn the dryer off.
2. Unplug from the wall outlet for 2 minutes.
3. Plug back in and select a short timed-dry cycle to test.

If the error reappears, use the specific troubleshooting below.

E01 — Control Board Error

The main electronic control board has detected an internal fault or communication failure.

Common causes:

• Power surge damage to control board components
• Failed relay or capacitor on the board
• Firmware glitch (rare but possible after power outage)
• Wiring harness disconnection between UI board and main board

How to fix:

1. Unplug the dryer for 5 minutes to allow a full firmware reset. This clears transient glitches that a quick power cycle may not.
2. Check the ribbon cable between the UI (display) board and the main control board — reseat both ends firmly.
3. Inspect the main board for visible damage: burnt traces, bulging capacitors, or darkened components.
4. Main control board replacement (part 00-706424) costs $200–$400. UI board (part 00-706425) costs $120–$250.

Pro tip: If E01 appeared immediately after a thunderstorm or power flicker, a surge protector may save future board replacements. Bosch recommends a dedicated 240V surge protector for their dryers.

E04 — Heating System Error

The dryer is not reaching the target temperature within the expected time. On heat pump models, this relates to the refrigerant circuit. On older condensation models, it relates to the electric heating element.

Common causes (heat pump models):

• Compressor failure or low refrigerant charge
• Clogged condenser fins (lint buildup restricts airflow over the heat exchanger)
• Failed compressor start relay or overload protector
• Evaporator coil icing (insufficient defrost cycle)

Common causes (conventional condensation models):

• Heating element failure (open circuit)
• High-limit thermostat tripped
• Failed temperature sensor

How to fix (heat pump models):

1. Clean the heat exchanger filter — open the lower access panel and slide out the self-cleaning condenser filter. Rinse under running water and let it dry completely before reinstalling. This should be done monthly.
2. Check the condenser fins for lint accumulation. Use a soft brush or vacuum with a brush attachment to clean between the fins.
3. Listen for the compressor — it should hum steadily during operation. A clicking-then-silence pattern indicates the compressor is trying to start but failing (start relay or overload issue).
4. Compressor replacement (part 00-752879) is $350–$600. Start relay kit (part 00-648907) is $40–$70.

How to fix (condensation models):

1. Test the heating element for continuity — should read 10–30 ohms. An open reading means the element has burned through.
2. Check the high-limit thermostat (part 00-619456) with a multimeter — it should be closed circuit at room temperature.
3. Heating element (part 00-649763) costs $80–$150.

E05 — Moisture Sensor Error

The moisture sensor that measures how dry the clothes are is not providing a valid signal.

Common causes:

• Mineral buildup on the moisture sensor bars (especially in hard water areas like the Bay Area)
• Sensor wire disconnected
• Control board sensor input failure

How to fix:

1. Locate the moisture sensor bars — two metal strips inside the drum, usually near the lint filter opening.
2. Clean the sensor bars with a soft cloth dampened with white vinegar or rubbing alcohol. Hard water mineral deposits create an insulating layer that prevents the sensor from reading moisture accurately.
3. If cleaning does not help, check the wiring connector at the back of the sensor. Vibration can loosen the plug over time.
4. Sensor assembly (part 00-612644) costs $25–$50.

Bay Area note: San Jose and Fremont have particularly hard water. If you are in these areas, clean the moisture sensor bars monthly to prevent E05 and inaccurate drying times.

E08 — Drum Motor Error

The drum motor is not rotating or is drawing excessive current.

Common causes:

• Drum belt broken or slipped off the pulleys
• Drum motor failure (brushes worn or winding fault)
• Drum bearing seizure
• Motor capacitor failure (on capacitor-start motors)

How to fix:

1. Open the dryer door and try turning the drum by hand. It should rotate smoothly with moderate resistance from the belt.
2. If the drum spins freely with no resistance, the belt is broken. On Bosch dryers, the belt (part 00-649054) wraps around the drum, under a tension pulley, and around the motor pulley. Replacement costs $20–$40 for the belt.
3. If the drum does not turn or feels gritty/stiff, the drum bearing or support rollers may be failing.
4. Listen for a humming sound from the motor when the cycle starts — a hum without rotation means the motor is locked mechanically or the start capacitor has failed.
5. Motor replacement (part 00-145424) runs $150–$300.

E09 — Drain Error (Condensation Models)

On condensation dryers (both heat pump and conventional), moisture extracted from clothes collects in a condensation tank. E09 means the tank is full or the drain pump cannot empty it.

Common causes:

• Condensation collection tank is full (must be emptied manually if not plumbed to a drain)
• Drain pump failure
• Clogged drain line (if the dryer is plumbed to a household drain)
• Float switch malfunction in the collection tank

How to fix:

1. Pull out the condensation collection tank (located at the top of most Bosch models) and empty it. This is normal maintenance for condensation dryers not connected to a drain.
2. If the tank was not full but E09 appeared, the drain pump or float switch is the issue. The float switch tells the board when the tank is full — a stuck float triggers E09 even with an empty tank.
3. Clean the condensation tank and its float mechanism under running water to remove lint and residue.
4. If you have plumbed the dryer to a household drain, check the drain line for kinks or blockage.
5. Drain pump (part 00-647192) costs $50–$90.

E12 — Temperature Sensor Error

The NTC temperature sensor is reading out of range — either shorted or open circuit.

Common causes:

• Temperature sensor (NTC thermistor) failure
• Sensor wire damaged or disconnected
• Corrosion at the sensor connector

How to fix:

1. Locate the temperature sensor — a small probe mounted in the drum air inlet or on the heater housing.
2. Measure resistance at the sensor terminals: expect approximately 10,000 ohms (10kOhm) at room temperature (68F). A reading of 0 (shorted) or infinite (open) confirms sensor failure.
3. Check the wiring and connector for damage or corrosion.
4. NTC sensor (part 00-618916) costs $15–$30.

E13 — Airflow Restriction

The dryer detects insufficient airflow through the system. Critical for heat pump models where airflow is essential for efficient heat exchange.

Common causes:

• Lint filter completely clogged (the most common cause)
• Heat exchanger filter clogged with lint
• Exhaust duct blocked or crushed (on vented models)
• Condenser fins covered in lint (heat pump models)

How to fix:

1. Clean the lint filter after every load — this is non-negotiable for Bosch dryers. A clogged lint filter immediately reduces efficiency and triggers E13.
2. On heat pump models, clean the self-cleaning condenser filter monthly. Open the lower panel, slide out the filter, and rinse under water.
3. Vacuum the condenser fin area with a soft brush attachment.
4. If using a vented model (rare in Bosch lineup), check the exhaust duct for kinks, crushed sections, or lint blockage. The exhaust run should not exceed 25 feet.

E21 — Door Switch Error

The dryer cannot confirm the door is closed.

Common causes:

• Door not fully latched
• Door switch failure
• Wiring issue to the door switch
• Door strike or catch broken

How to fix:

1. Close the door firmly until you hear a solid click.
2. Inspect the door catch and strike for damage. Plastic door catches can crack over time.
3. Test the door switch with a multimeter — it should show continuity when pressed (door closed) and open when released.
4. Door switch (part 00-616099) costs $15–$25. Door catch (part 00-648903) costs $10–$20.

E33 — Heat Pump Pressure Error

Specific to heat pump dryers — the refrigerant system pressure is outside the normal operating range.

Common causes:

• Refrigerant leak in the sealed system
• Compressor valve failure
• Condenser or evaporator blockage
• Ambient temperature too low (heat pump dryers require room temperature above 41F / 5C)

How to fix:

1. Check that the laundry room temperature is above 41F. Heat pump dryers cannot operate efficiently in cold garages or unheated spaces — the refrigerant pressure drops below the minimum threshold.
2. Ensure adequate ventilation around the dryer. Heat pump models need at least 4 inches of clearance on all sides.
3. If the room is warm and ventilation is adequate, E33 indicates a sealed-system problem requiring a refrigerant-certified technician. This is not a DIY repair.
4. Sealed system repair typically runs $400–$700. If the compressor itself has failed, replacement may approach the cost of a new unit.

Home Connect Smart Diagnostics for Dryers

Bosch Home Connect (500 and 800 Series, 2020+) provides enhanced dryer diagnostics:

1. Drying performance tracking: The app monitors cycle efficiency over time, alerting you to gradual degradation that signals lint buildup or component wear before an error code appears.
2. Filter cleaning reminders: Automated reminders based on actual usage frequency.
3. Error history with context: Stores error events with cycle type, load size setting, and temperature — invaluable for diagnosing intermittent issues.
4. Energy monitoring: Track per-cycle energy consumption. A sudden increase often precedes a formal error code.

Bosch Heat Pump vs. Condensation vs. Vented: Know Your Model

Bosch sells three dryer types in the US market, and troubleshooting differs:

• Heat pump (WTX/WTW prefix): No vent, uses refrigerant cycle. Most energy-efficient. Error codes E33 and compressor-related issues are unique to these.
• Condensation (WTG prefix): No vent, uses electric heating element. Simpler than heat pump but less efficient. Requires condensation tank emptying.
• Vented (WTZ prefix, discontinued): Traditional vented design, rare in current lineup. Standard heating element troubleshooting applies.

Your model prefix (first 3 characters of the model number) tells you which type you have.

Frequently Asked Questions

Q: How do I reset my Bosch dryer after an error? A: Power off, unplug for 2 minutes, plug back in, and run a short timed-dry cycle. For persistent errors, hold the Start button for 5 seconds before powering off. Error codes clear after the underlying issue is resolved.

Q: Why does my Bosch heat pump dryer take so long to dry? A: Heat pump dryers operate at lower temperatures than conventional dryers (about 140F vs 180F), so cycles are inherently longer — typically 90–120 minutes for a full load. However, if drying times have increased beyond normal, the heat exchanger filter likely needs cleaning. Clogged condenser fins are the #1 cause of poor heat pump dryer performance.

Q: Do I need to empty the water tank every cycle? A: Yes, unless your Bosch condensation or heat pump dryer is plumbed directly to a drain. The condensation tank collects moisture from each load. If it fills completely, the dryer stops with E09. Most households empty the tank every 1–2 loads.

Q: Can I put a Bosch ventless dryer in a closet? A: Yes, but with conditions. Bosch ventless dryers are popular in Bay Area apartments and condos specifically because they need no external vent. However, the closet needs adequate ventilation — at least 200 square inches of airflow opening. Without it, the dryer overheats and triggers E04 or E13 errors. Leave the closet door louvered or cracked during operation.

Q: Is a Bosch heat pump dryer worth repairing if the compressor fails? A: Compressor replacement runs $400–$700. Since a new Bosch heat pump dryer costs $1,100–$1,500, repair makes economic sense if the unit is under 6–7 years old and the rest of the machine is in good condition. Beyond 8 years, replacement may be more cost-effective.

When to Call a Professional

Safe DIY tasks include lint filter cleaning, condensation tank emptying, moisture sensor cleaning, and basic door latch fixes. Call a professional for:

• E01 control board errors — Board diagnosis and replacement requires proper part matching.
• E04 heat pump compressor issues — Sealed refrigerant system work requires EPA Section 608 certification.
• E08 with seized drum — Bearing replacement requires significant disassembly.
• E33 refrigerant pressure errors — Only certified technicians can work on sealed systems.
• Any electrical burning smell — Disconnect power immediately.

Bosch dryer showing an error code you cannot clear? EasyBear technicians specialize in Bosch heat pump and condensation dryers — the ventless European-style units that most general repair companies are unfamiliar with. We offer free diagnostic visits and carry common Bosch dryer parts for same-day repair. Every job includes our 90-day parts and labor warranty. Schedule your free diagnosis today.