E31
Bosch Dryer
Severity:What Does This Error Mean?
E31 on a Bosch heat pump dryer means a fault has been detected in the refrigerant circuit. This is the sealed system that circulates refrigerant between the evaporator and condenser coils. E31 requires a certified technician — refrigerant systems cannot be worked on without specialist tools and certification.
Affected Models
- Bosch WQB145B0GB
- Bosch WTH84000GB
- Bosch Serie 6 Heat Pump Dryer
- Bosch Serie 8 Heat Pump Dryer
Common Causes
- Refrigerant leak in the heat pump circuit
- Evaporator or condenser coil in the heat pump circuit blocked or frosted over
- Pressure switch or sensor in the refrigerant circuit faulty
- Heat pump expansion valve stuck or blocked
- Compressor not building sufficient pressure in the circuit
How to Fix It
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Clean the lint filter and condenser unit.
A frosted or blocked evaporator coil inside the heat pump circuit can trigger E31. Ensuring the airflow is unrestricted sometimes allows the circuit to recover.
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Allow the dryer to rest unplugged for 30 minutes.
If the evaporator has frosted over, the rest period allows it to thaw.
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If E31 returns, book a Bosch service visit.
The technician will connect pressure gauges to the refrigerant circuit to measure charge and diagnose the fault.
When to Call a Professional
E31 requires a Bosch-authorised technician with F-Gas certification. Refrigerant handling is legally regulated — do not attempt to diagnose or repair the refrigerant circuit yourself.
Frequently Asked Questions
Is a refrigerant leak in a dryer dangerous?
The refrigerants used in Bosch heat pump dryers (typically R134a or R290) are not toxic, but R290 (propane) is flammable. If you smell something unusual from the dryer, stop using it and call a technician. A refrigerant leak also means the dryer will not dry effectively.