Bosch Singular 4000 - Page 32

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Service Manual
Singular Combi Boiler - BTC 439002301 A (12.2021)
A9 Error - Wire Check
1. Check if the heating water sensor connector is disconnected
Figure 29
A9 Error - Exhaust Temperature Sensor Check
1. Check if the heating water sensor is defective
— Defective: OL
— Normal: 86 °F: 40 kΩ
140 °F: 12.4 kΩ
185 °F: 3.9 kΩ
Figure 30
kΩ