Bosch 250SX Service Bulletin

TWH-G2-23 | 2400E, 2400EO, 250SX, 250SXO, 635ES, 635ESO
Service bulletin
Replacing and cleaning electrodes
Introduction
The electrode set may need to be cleaned or replaced if the

heater has frequent EC error codes or does not spark.
Tools needed:
Philip head screw driver

8mm open end wrench or small adjustable wrench

Steel wool for cleaning electrodes

Removing electrode set
1. Turn off gas to heater using installer supplied manual shut off
valve.
2. Turn power switch to the off (O) position and unplug heater.
3. Remove cover per chapter 4 in installation manual.
4. Remove brass phillips-head screws to release holding bracket.
Accessing electrode set
Holding Holding
bracket bracket
screws screws
Air intake Air intake
duct duct
Air intake Air intake
duct screws duct screws
5. Remove air intake duct: remove two philips-head screws on the
bottom of the air intake duct and then pull forward.
NOTE: There is a thin black oring between the air intake duct and
the gas/air mixer that may fall out.
6. Disconnect three yellow wires connected to the bottom of the
electrode set.
7. Remove two 8mm retaining nuts.
Electrode connectors
8mm ret t ain- 8mm retain- t
ing nuts ing nuts
Ignitor rods Ignitor rods
connectors connectors
Flame sensor Flame se e nsor e
rod conn n ector rod connector n
8. Lower the electrode set slowly and rotate inward to remove.