Bosch Appliances GWH-635-ES manual Troubleshooting Display Cause Solution, Chapter

Troubleshooting

Display	Cause	Solution
E9	Temperature limiter opened circuit	Check connections.*
	(overheat). Trips at 220F (104C).	Check heat exchanger condition.*
EA	No ionization during safety time (safety time	Check gas pressure.*
	out).	Check that gas is not diluted with air, as a result
		from recent gas pipeline rework.*.
		Check if vent terminal is blocked (especially when
		the appliance starts up for some seconds and then
		looses ionization signal).*
		Check ionization electrode.*
		Check for a proper ground.*
FA	Leakage error (gas valves do not close gas	Check gas valve and control unit.*
	circuit).
F7	Ionization error (flame sensing at stand-by).	Check control unit.*
E0	Internal software/hardware failure.	Check control unit.*
A7	Hot water temperature sensor/receiver	Check water temperature sensor/receiver and
	defect (from control unit).	connections.*
		Check room area temperature where heater is
		located, it must be above 36°F (2°C)
A9	Hot water temperature sensor/receiver mis-	Check that the water temperature sensor/receiver is
	assembled (from control unit).	properly assembled in the water pipe.*
		Check if vent terminal is blocked or if vent terminal is
		according with chapter 2.9.*
		In case of high altitude installation confirm that
		necessary adjustment steps have been taken.*
C1	FAN rotation too low at start-up (from	Check supply voltage.*
	control unit).	Check fan and connections.*
		Check control unit.*
		Check if vent terminal is blocked or if vent terminal is
		according with chapter 2.9. *
		Check CO2 levels (see chapter 9).*
C6	FAN rotation too low at operation (from	Check supply voltage.*
	control unit).	Check fan and connections.*
		Check control unit.*
		Check if vent terminal is according with
		chapter 2.9.*
C7	No rotational speed sensor signal from FAN	Check fan and connections.*
		Check control unit.*
		Check CO2 levels (see chapter 9).*
CA	Water flow signal over specified maximum	Check water valve and flow sensor.*
	value
E2	Inlet temperature sensor fault	Check water temperature sensor/receiver and
		connections.*
		Check room area temperature where heater is
		located, it must be above 36°F (2°C)
A2	Overheat protection fault	Check connections to the overheat protection.*
		Check sensor continuity.*
		Check heat exchanger sealings and walls.*

Table 5

* By installer or service technician only.

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