Bosch C 950 Installation Manual page 53

Display Cause
F1 Parameter in memory not found
F2 Internal Operations error
F3 Internal memory parameter error
F4 Internal memory error
F5 Analog test fail
F6 Gas type parameter error
E7 Appliance parameter not defined
F0 Burner Control routine state error
E5 Burner Control error
E6 Burner Control routine check sum error
F8 Fan stopping error
F9 Gas Control error
F7 Ionization error at standby.
FA Gas leakage error, gas valve circuit not
closing properly.
Table 54
* By installer or service technician only.
Greentherm
Solution
1. Replace ECU (Electronic Control Unit) if there are repeated errors.
1. Check primary fan cable harness
2. Check fan rotation in standby
3. Check proper function of primary fan
4. Replace ECU (Electronic Control Unit)
1. Check Gas Valve cable harness (connection to gas valve and to ECU)
2. Check Gas Valve (Replace if necessary)
3. Replace ECU (Electronic Control Unit)
1. Loose connection to the flame ionization rod. Verify that the thinner wire leading from the
control unit is securely connected to the set of electrodes located on the lower front of the
heat exchanger.
2. Flame ionization rod or control unit may be damaged. Contact Bosch Water Heating for
further instruction.
1. Disconnect power supply cord and check wire connections on gas valve and the two
connectors on the control board.
2. Flow water out of a hot water tap above the minimum activation point of 0.5 GPM.
Measure voltage at the gas valve wire plug connection. The voltage should measure 24VDC
between the left pair of wires and 24VDC between the right pair of wires when the unit is
operating. If voltage is not proper, contact Bosch Water Heating for further instruction.
3. Gas valve may be defective, contact Bosch Water Heating for further instruction.
Problem solving | 53
6 720 805 440 (2014/11)