Bosch Therm C1050ES Technical Service Bulletin page 3

3 | Replacing The Control Unit
C 1050 ES or 940 ES/ESO with surface mount outlet
temperature sensor
Natural
Gas
C 1050 ES or 940 ES/ESO with immersed outlet temperature
sensor
Natural
Gas
Replacing control unit
Once the appropriate jumpers have been determined, remove

rear cover of replacement control unit.
Install jumpers in the proper location on PCB.

Connect green ground wire from power cord to replacement

control board with Phillips head screw. (Fig. 3, pos. 8).
Reconnect black and white power cord wires to terminal

block on replacement control unit; Black -L (Load), White - N
(Neutral). Secure to terminal block by tightening flat head
screws. (Fig. 3, pos. 7).5. Reconnect yellow/green striped
ground wire to spade connection on replacement control
board. (Fig. 3, pos. 6).
Reattach large ignition wires to replacement control board (no

polarity). (Fig. 3, pos. 5).
 Reconnect small electrical strip connector to replacement
control board. (Fig. 3, pos. 4).
Data subject to change without notice | Printed in the USA | BTC 740002317 C | 06.2012


Figure 7

Liquid

Propane


Figure 8
Liquid
Propane
Reconnect medium sized electrical strip connector to
replacement control board. (Fig. 3, pos. 3).
Reconnect two large electrical strip connectors to replacement
control board. (Fig. 3, pos. 2).
Reseat rubber wire restraints in control unit. (Fig. 3, pos. 1).
Replace rear cover on unit using 6 Phillips screws. (Fig. 2, pos.
3).
Place control unit back into water heater and secure with 3
Phillips head screws. (Fig. 2, pos. 1).
Plug water heater power cord back into electrical outlet and
push On/Off button on water heater to "ON".
Bosch Thermotechnology Corp.
50 Wentworth Avenue
Londonderry, NH 03053
Tel: 1-800-283-3787
Fax: 1-603-965-7581
www.bosch-climate.us
Technical Service Bulletin
Bosch Thermotechnology Corp.