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Troubleshooting
37
C1 Fan rotation too low on startup.
(part# 8707204039)
1. Disconnect power supply cord. Check wire
connections on back side of fan and the two large
wire connectors on the control unit. Removal of
lower access panel on control unit is necessary to
access connectors.
2. Verify that supply voltage is 120VAC and is
properly grounded.
3. Verify that venting meets specifications outlined
in chapter
3.6. Long vent lengths, venting with more
than three elbows, blocked vent or combination
venting may cause this failure. Verify backdraft
flapper inside flue gas collector is not stuck shut.
4. Check gas pressure. See chapter
3.8. Low gas
pressure may cause the fan to change its speed to
meet desired temperature.
5. Possible defective control unit. Call Bosch Water
Heating for further instructions.
C6 Fan rotation too low in operation
(part# 8707204039)
1. Disconnect power supply cord. Check wire
connections on back side of fan and the two large
wire connectors on the control unit. Removal of
lower access panel on control unit is necessary to
access connectors.
2. Check supply voltage is 120VAC and is properly
grounded.
3. Verify that venting meets specifications outlined
in chapter
3.6. Long vent lengths, venting with more
than three elbows, blocked vent or combination
venting may cause this failure. Verify backdraft
flapper inside flue gas collector is not stuck shut.
4. Ensure intake and exhaust terminations maintain
the required clearances stated in the manual (
Fig.
17
and Table 6 on page 17). Cross
contamination between intake and exhaust may
cause the fan to alter its rotational speed.
5. Check gas pressure. See chapter
3.8*. Low gas
pressure may cause the fan to change its speed to
meet desired temperature.
6. Possible defective control unit. Call Bosch Water
C7 No rotational speed sensor from fan.
(part# 8707204039)
1. Disconnect power supply cord. Check wire
connections on back side of fan and the two large
wire connectors on the control unit. Removal of
lower access panel on control unit is necessary to
access connectors.
2. Check supply voltage is 120VAC and is properly
grounded.
3. Possible defective component in fan. Call Bosch
Water Heating for further instructions.
CA Water flow signal over specified maximum
value.
(part# 8708505016)
1. Disconnect power supply cord and check wire
connections on water valve and the two connectors
on the control board.
2. Excessive water pressure and flow. Ensure water
pressure is less than 150psi and flow rate is less
than 10 gallons per minute.
Display Cause Solution
Table 12
* By installer or service technician only.