Bosch 425HN Reference manual

Service bulletin

Replacing control box

CT-27 | 1600H, 425HN

Tools needed:

Phillips head screwdriver

Needle-nosed pliers

Removing ignition unit

1. Close installer supplied cold water shut off valve to water heater.

2. Remove front cover of heater. (See instructions in the installa-

tion manual)

3. Remove single ignition wire connection (to spark electrode)

from upper left corner of ignition unit. Unclip wire from bracket

on top of ignition unit (425HN models only). (See Fig. 1)

4. Remove multiple wire connector from lower right corner of

ignition unit by gently pulling outwards with needle-nosed pliers.

(See Fig. 1)

5. Remove screw with ground wire connection from upper right

corner of ignition unit Metal bracket and ignition unit will drop

out of heater.

6. Remove ignition unit from metal bracket.

Control box (425HN model shown) Figure 1

Installing ignition unit

1. Insert tab on lower left of ignition unit into slot in lower left of

metal bracket.

2. Mount ignition unit with bracket to heater by inserting screw

into upper right hand corner.

Note: Feed screw through ground wire eyelet with washer before

threading through ignition unit to heater. (See Fig. 1)

3. Press multiple wire connector into lower right of ignition unit.

4. Push ignition wire on to single terminal in top left corner of

ignition unit. Clip wire into bracket on top of ignition unit

(425HN models only).

5. If a replacement hydro generator (black and red lead wires) was

sent as a temporary solution for ignition failure, please reinstall

original hydro generator, part# 8707406071 (blue and brown

lead wires).

6. Install front cover, open cold water supply and return heater to

service.

1 2 |TWH-G2-06 | 2400E, 2400EO, 635ES, 635ESO, 250SX, 250SXO Service bulletin

Data subject to change without notice | Printed in the USA | 1.2007 Bosch Water Heating

BBT North America Corporation

Bosch Group

Bosch Water Heating

340 Mad River Park

Waitseld, VT 05673

Telephone 800-642-3111

Fax (802) 496-6924

techsupport@boschhotwater.com

This manual suits for next models

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