Bosch Singular 4000 - Page 49

| 49
Service Manual
Singular Combi Boiler - BTC 439002301 A (12.2021)
E3 Error - Wire Check
1. Check the connection of the wire.
Figure 72 Control Board
Figure 73 Return Sensor
E3 Error - Return Sensor Check
1. Measure the resistance of the Return sensor. If the resistance is not normal,
replace the Return sensor.
— Disconnection: OL
— Normal: 86 °F: 40 kΩ
140 °F: 12.4 kΩ
185 °F: 3.9 kΩ
Figure 74
KΩ
E3 Error - Disconnection Check
1. Check if the Hot Water Thermistor is disconnected.
— Disconnection: OL
— Normal: 86 °F: 40 kΩ
140 °F: 12.4 kΩ
185 °F: 3.9 kΩ
Figure 75
kΩ
E3 Error - Short Circuit Check
1. Check if the Return sensor has short-circuited.
— Short circuit: 0 Ω
— Normal: 86 °F: 40 kΩ
140 °F: 12.4 kΩ
185 °F: 3.9 kΩ
Figure 76
Ω
E3 Error - Control Board Check
1. If the wire connection and the resistance of the Hot Water Thermistor are
normal, replace the control board.