Technical Service Bulletin:
C6 & C7 Error Code Troubleshooting
Models: C1210ESC, C1210ES, C1050ES, C950ES, 940ES, 940ESO, 830ES, 2400ES,
2700ES, 715ES, C800ES, C920ES/ESC, Integra 500, Evolution 500
This procedure must be performed by a qualiﬁ ed technician.
120 VAC present in wire connections. Use caution
Follow the procedures below and report results to Bosch Technical
Support. This will assist in determining the cause and solution to the
C6 and C7 error codes
These errors are fan-related error codes with the following
C6 error indicates the primary fan rotation is too low during
C7 error indicates there is no primary fan rotation sensed
during an attempted start-up.
Primary Fan Assembly
The primary fan is a 120 volt AC fan that receives power from
the main control board.
The primary fan has its own built-in circuit board which relays
information and signals back to the control board.
Phillips head screwdriver
Press the reset button on the control panel of the heater to
attempt to clear the error code. If the error code does not reset
or continues to reoccur, proceed with the following trouble-
Conﬁ rm that the exhaust vent is not blocked and does
not exceed the speciﬁ ed maximum length as shown in the
Ensure that the 3 foot minimum separation between air intake
and exhaust vents is met (applies to a twin pipe vent system).
Verify the heater is plugged into a properly grounded 120V AC
Supply the heater with a steady supply voltage. It is
recommended to supply electricity from a dedicated electrical
circuit with no other major appliances on the same circuit.
Shut off power to the heater and unplug from electrical outlet.
Remove cover per installation manual.
Remove the black plastic intake (Fig.1, pos.1) that is secured
with three Phillips head screws to the fan (Fig.1, pos.2).
Check the wire connection to the fan. The wire connection is
located on the back, left hand side of the fan housing. (Fig. 2).