HVACopediaViessmann · Boiler
F.669 DHW reheating sensor TS4 short circuit
What the control is telling you
No solar preheating function.
Applies to: Vitodens 200-W B2HE 85, 120, 150, 199
Likely causes
- Shorted TS4
Test and repair steps
- Check temperature sensor TS4.
Models that show this code
4 models in Vitodens 200-W B2HE
Other codes on the same units
- F.63 Flue gas temperature limiter tripped
- F.666 DHW preheating sensor TS3 open circuit
- F.667 DHW preheating sensor TS3 short circuit
- F.668 DHW reheating sensor TS4 open circuit
- F.67 Ionization current outside permitted range
- F.670 Buffer sensor TS3 open circuit
- F.671 Buffer sensor TS3 short circuit
- F.672 Thermostat-function sensor TS3 open circuit
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Source: Viessmann Vitodens 200-W B2HE 85/120/150/199 Service Instructions 6167 813-24 (09/2026), Fault messages, p.62-73. Summarized in our own words; check the original manual for your model.
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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.