Bosch Dryer Not Heating — Heat Pump, Element & Sensor Troubleshooting
A Bosch compact dryer that runs without heating produces cold or room-temperature air — clothes tumble but never dry. This is distinct from "not enough heat" (covered separately). Zero heat means the primary heating system has completely failed.
Identify Your Heating System
- WTW series (heat pump): Uses refrigerant compressor — no heating element. Zero heat = compressor not running.
- WGA series (condenser): Uses electric heating element. Zero heat = element burned out or no power to element.
Check model number on the sticker inside the door frame to identify your type.
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Gas leak detector ($130), thermal fuse tester ($95), belt tension gauge, and vent inspection camera ($180). Our technician arrives with $15K+ in professional tools — your diagnostic is free.
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Most Common Causes
1. Clogged Condenser Triggering Thermal Cutout (30% of cases)
Heavy lint on condenser fins causes the heat pump to overheat and trip its thermal protection. Once tripped, the compressor stops and the dryer circulates unheated air. May display E:04. After cooling (30–60 min), it resets and heats briefly before tripping again.
Fix: Clean condenser (pull out from front bottom panel, vacuum fins thoroughly).
DIY Difficulty: Easy Parts Cost: $0 Professional Repair Cost: $89–$150
2. Compressor Failure (25% of cases — WTW only)
If the compressor has failed electrically or mechanically, zero heat is produced. No compressor hum from the base of the dryer. E:04 error code.
Diagnosis: Start a cycle, put your ear near the base. Should hear steady hum within 2 minutes. Complete silence = compressor not starting. Could be: failed start relay ($30–$60), failed compressor windings ($300–$600), or blown compressor thermal fuse ($15–$25).
DIY Difficulty: Professional (sealed system) Parts Cost: $30–$600 Professional Repair Cost: $200–$900
3. Heating Element Burnout (20% of cases — WGA only)
The resistive element in WGA condenser dryers can burn out like any heating element. Test with multimeter — should read 20–40 ohms. Open circuit = burned out.
Access: Rear panel removal (Torx T20) reveals the element housing.
DIY Difficulty: Moderate Parts Cost: $50–$100 Professional Repair Cost: $150–$280
4. NTC Sensor Causing Board to Block Heating (15% of cases)
If an NTC sensor reads extreme values (shorted = very low resistance = board sees extreme overheat), the control board refuses to engage heating as a safety measure. Error E:03 may display.
Fix: Replace faulty NTC sensor ($15–$35).
DIY Difficulty: Easy-Moderate Parts Cost: $15–$35 Professional Repair Cost: $120–$200
5. Control Board Heating Circuit Fault (10% of cases)
The board relay or MOSFET controlling the heating system fails open — no signal sent to compressor or element. Board replacement required.
DIY Difficulty: Moderate Parts Cost: $150–$350 Professional Repair Cost: $280–$500
Step-by-Step Diagnosis
- Identify model type — WTW (heat pump) or WGA (condenser element).
- Start a cycle. After 15 min, feel air in drum — warm or cold?
- Listen for compressor (WTW) — hum from base.
- Check for error codes — E:04 (heat pump), E:03 (sensor).
- Clean condenser — first fix to try on any heat complaint.
- WGA: Test element resistance — 20–40 ohms normal.
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Gas dryers carry carbon monoxide and explosion risk. Even electric dryers involve 240V circuits that can deliver a fatal shock. Our techs are licensed and insured — let them handle the risk.
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DIY Fix vs Professional Repair
| Issue | DIY? | Parts Cost | Professional Cost |
|---|---|---|---|
| Clogged condenser | Yes | $0 | $89–$150 |
| Compressor | Professional | $30–$600 | $200–$900 |
| Heating element (WGA) | Moderate | $50–$100 | $150–$280 |
| NTC sensor | Easy-Moderate | $15–$35 | $120–$200 |
| Control board | Moderate | $150–$350 | $280–$500 |
FAQ
Q: Is it worth replacing the compressor on an old Bosch dryer?
Compressor replacement costs $500–$900 professionally. If your dryer is under 8 years old, repair is likely worthwhile (new unit costs $1,200–$1,800). Over 10 years old, consider replacement.
Q: My Bosch dryer heats for 10 minutes then goes cold. What's happening?
The heat pump thermal cutout is tripping from overheating — almost always caused by a clogged condenser restricting airflow. Clean the condenser first.
Bosch dryer not heating? Our technicians diagnose heat pump and condenser systems on all compact models. Schedule a repair →
