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Troubleshooting; Introduction; No Spark At Pilot With Water Flow; Spark Appears When Hot Water Is Turned On, But Pilot And Burners Will Not Ignite - Bosch Aquastar GWH 1600 H N User Manual

Hydro-generated ignition suitable for heating potable water only not approved for space heating or preheated water applications
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Many of the questions customers ask regarding
operation of this unit can be answered by following the
troubleshooting steps as outlined below. Visit our web
site at for more detailed
troubleshooting. For best results, perform each step
before proceeding to the next. The suggested solutions
may require that the cover be taken off (See chapter

No spark at pilot with water flow

• 1. Verify the ON/OFF button, located behind the flip
down cover plate, is completely depressed in the ON
position (Position
Fig. 17.
• 2. Verify the cold water supply is connected to the
right side rear of the water valve.
• 3. Close installer supplied cold water shut off valve (if
none installed, install before proceeding). Open all
hot water taps supplied by the heater. Wait 5
minutes and check all taps. Any water running is a
sign of a plumbing crossover. Consult a local
plumber or service person for help in correcting a
plumbing crossover.
• 4. Confirm that there is an adequate flow rate. With
the temperature adjustment knob on the unit
positioned all the way clockwise, a 1/2 gallon per
minute (GPM) flow rate is required for heater
activation. Fully open a hot water faucet and fill a
quart container. If the container fills in 30 seconds or
less, the flow rate (1/2 GPM) is sufficient to activate
the water heater.
NOTE: When the dial is turned all the way
counterclockwise, a flow rate of 1.1 GPM is required
for heater activation.
• 5. Inspect the water path for obstructions. Make sure
all outlets (i.e. showerheads, faucet aerators and
whole house filters) are clear of debris. Inspect and
clean the water heater's inlet filter screen. See
chapter 5.2.
• 6. Verify all wire connections are secure, paying
close attention to the wire connection between the
piezzo electrode and the electronic control box.
• 7. Check for voltage at the hydro-generator.
Disconnect plug connector on wires leading from
hydro-generator (approximately 3" from hydro-
generator). Verify voltage on hydro-generator side of
plug connector with hot water running. The voltage
reading should be 1.6VAC or greater. If voltage is
lower, then remove and flush the hydro-generator.
Reinstall hydro-generator and take another voltage
reading. If voltage is at least 1.6VAC, proceed to next
step. If voltage is still low, hydro-generator may be
6 720 608 032
). See chapter chapter 4.2,
damaged/defective. Visit
to purchase replacement part, or call Bosch Water
Heating at 800-642-3111 for replacement part if still
under warranty.
• 8. If using a power vent, check the safety spillage
switch reset button (the safety spillage is wired
through the water heater's thermocouple circuit).
The safety spillage switch should be located at the
top of the water heater close to the draft diverter.
Consult power vent manual for more detailed
• 9. Verify the spade connectors on the two overheat
sensors (ECO) & the flue gas sensor are plugged in
securely and their terminals are free of corrosion. The
terminals can be cleaned with a pencil eraser. The
ECO's are located on the lower left hot water outlet
pipe and the upper right side of heat exchanger. The
flue gas sensor is located on the upper right side of
draft diverter.
• 10. Verify the microswitch located on bottom of gas
valve is firmly mounted and wire clip connector is
• 11. Electronic control box may be damaged or
purchase replacement part, or call Bosch Water
Heating at 800-642-3111 for replacement part if still
under warranty.
Spark appears when hot water is
turned on, but pilot and burners
will not ignite
• 1. Verify gas type indicated in the rating sticker
located on the cover's right hand side, coincides with
the gas type you are using. NG is a natural gas unit
and LP is for liquid propane (see chapter 2.2).
• 2. If the unit was just installed or the gas lines have
been worked on, there may be air in the gas line.
Bleed out the air trapped in the gas line by turning the
hot water faucet on and off until the pilot flame/
burners ignite. (Please note: depending on how
much air is in the line this could take numerous cycles
of turning the faucet on and off).
• 3. Verify gas supply is on at Natural Gas meter or
Propane tank. Make sure all manual gas shut off
valves are open.
• 4. Have a licensed gas technician confirm adequate
gas pressure at the inlet tap (See gas requirements
in chapter 2.1). If gas is not present, verify
manufacturer supplied Maxitrol regulator is in the
upright position.
The arrow on the back of the
regulator should point in the same direction as gas

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