Bosch Heat Pump Error Codes & Fix Guide
Bosch Heat Pump Error Codes & Fix Guide (Ultimate HVAC Guide)
When a Bosch heat pump displays an error code, it’s not just a fault—it’s a precision diagnostic signal from a highly engineered system. Understanding these codes allows HVAC professionals and homeowners to quickly identify issues, reduce downtime, and avoid costly repairs.
This complete Bosch Thermotechnology heat pump error code guide covers everything—from basic explanations to advanced troubleshooting techniques used by professionals.
About Bosch Thermotechnology
Bosch Thermotechnology is part of the global engineering giant Bosch. Known for reliability and innovation, Bosch heat pumps (like Compress 3000, 5000, and 7000 series) are widely used across Europe and North America.
1. What Are Bosch Heat Pump Error Codes?
Bosch heat pumps feature advanced control systems that continuously monitor:
- Temperature sensors
- Refrigerant pressure
- Compressor operation
- Water flow rate
- Electrical components
When a fault occurs, the system displays:
- Error Codes (E / F codes) → System stops or limits operation
- Warning Codes → System continues but requires attention
2. Types of Bosch Heat Pump Faults
Electrical Faults
- Power supply issues
- PCB malfunction
- Relay failure
Sensor Faults
- Outdoor sensor failure
- Flow/return sensor issues
Refrigerant Faults
- Low refrigerant charge
- High pressure
- Compressor overheating
Hydraulic Faults
- Low water flow
- Pump failure
Communication Faults
- Indoor-outdoor communication failure
- Controller errors
3. Complete Bosch Heat Pump Error Code List
Critical Error Codes
| Code | Description |
|---|---|
| E01 | Flow temperature sensor fault |
| E02 | Return temperature sensor fault |
| E03 | Outdoor sensor fault |
| E04 | Evaporator sensor fault |
| E05 | Condenser sensor fault |
| E06 | Discharge temperature fault |
| E07 | Defrost sensor fault |
| E08 | Hot water sensor fault |
| E09 | Flow switch error |
| E10 | High pressure fault |
| E11 | Low pressure fault |
| E12 | Compressor overload |
| E13 | Expansion valve fault |
| E14 | Defrost failure |
| E15 | Freeze protection triggered |
| E16 | Pump failure |
| E17 | Communication error |
| E18 | Voltage fault |
| E19 | PCB fault |
| E20 | General system fault |
Warning Codes
| Code | Description |
|---|---|
| A01 | Temporary interruption |
| A02 | Defrost mode active |
| A03 | Compressor delay |
| A04 | Anti-freeze mode |
| A05 | System optimization |
4. Common Bosch Error Codes Explained
E10 – High Pressure Fault
Causes:
- Dirty condenser coil
- Blocked airflow
- Overcharged refrigerant
Fix:
- Clean outdoor unit
- Check fan motor
- Adjust refrigerant charge
E11 – Low Pressure Fault
Causes:
- Refrigerant leakage
- Expansion valve issue
Fix:
- Leak detection
- Recharge refrigerant
E09 – Flow Switch Error
Causes:
- Low water flow
- Blocked filter
Fix:
- Clean strainer
- Check pump
E12 – Compressor Overload
Causes:
- High pressure
- Electrical imbalance
Fix:
- Check compressor current
- Inspect capacitor
E17 – Communication Error
Causes:
- PCB failure
- Wiring issue
Fix:
- Check connections
- Replace control board
5. Advanced Troubleshooting Workflow
Step 1: Identify Error Code
Read from display panel.
Step 2: Reset System
- Turn OFF power
- Wait 5 minutes
- Restart
Step 3: Basic Inspection
- Power supply
- Water pressure
- Filters
Step 4: Sensor Testing
- Use multimeter
- Compare resistance values
Step 5: Refrigerant Diagnosis
- Check pressure gauges
- Inspect for leaks
6. Sensor Fault Diagnosis
Bosch systems use NTC sensors.
Common Issues:
- Open circuit
- Short circuit
Testing:
- Measure resistance
- Compare with temperature chart
7. Refrigerant & Pressure Issues
Symptoms:
- Poor heating
- Ice formation
- Frequent shutdown
Causes:
- Gas leakage
- Dirty coils
- Expansion valve blockage
Fix:
- Leak repair
- Recharge system
- Clean coils
8. Electrical & PCB Faults
Common Codes:
- E17
- E18
- E19
Causes:
- Voltage fluctuation
- PCB damage
Fix:
- Install stabilizer
- Replace PCB
9. Communication Errors
Causes:
- Wiring faults
- Controller issues
Fix:
- Inspect cables
- Replace faulty modules
10. How to Reset Bosch Heat Pump
Method 1:
Use reset button
Method 2:
Power OFF → Wait → ON
Method 3:
Reset via controller
11. Preventive Maintenance Checklist
Monthly:
- Check pressure
- Clean filters
Quarterly:
- Inspect wiring
- Test sensors
Yearly:
- Full servicing
- Refrigerant inspection
12. Pro HVAC Diagnostic Tips
Since you’re an HVAC professional, here are expert-level insights:
Superheat & Subcooling
- High superheat → low charge
- Low superheat → flooding
Delta T Monitoring
- Ideal: 5–10°C
Compressor Amp Analysis
- High amps → mechanical issue
Multi-Symptom Diagnosis
- High pressure + low airflow → dirty condenser
- Low pressure + frost → refrigerant leak
13. FAQ Section
Q1. What does E10 mean on Bosch heat pump?
It indicates high refrigerant pressure caused by airflow restriction or overcharging.
Q2. How do I reset a Bosch heat pump?
Turn off power, wait 5 minutes, and restart.
Q3. Why does low pressure error occur?
Due to refrigerant leaks or expansion valve problems.
Q4. Can I fix Bosch error codes myself?
Basic issues can be fixed, but complex faults require professionals.
Q5. How often should servicing be done?
At least once per year.
Final Thoughts
Bosch heat pumps are highly reliable systems, but like any advanced HVAC equipment, they require proper diagnostics when issues arise. By understanding Bosch error codes, you can quickly pinpoint faults, improve service efficiency, and reduce downtime.
