Bosch C1210ES Technical Service Bulletin

Technical Service Bulletin:
Checking and Replacing Temperature
Sensors
Models: C1210ESC, C1210ES, C1050ES, C950ES, 940ES, 940ESO, 830ES
Introduction
The inlet and outlet temperature sensors work together to

ensure the desired set temperature on the water heater is
reached accurately. The cold water sensor is located in the
water valve and the hot water sensor is clipped on the hot water
outlet pipe. Poor contact, corroded connections and/or a
defective sensor can result in undershooting, overshooting or
fl uctuation of the hot water temperature. In some cases, the
heater will lock out with an error code fault that requires
resetting.
Tools needed:
Phillips head screw driver

Multi-meter

Thermometer

Emery cloth

Preparation
1. Clear error codes with the reset button on the heater.
2. Push power button to turn water heater "OFF".
2. Loosen two Phillips head screws and remove front cover. (Fig. 1)
Step 1 Step 1
3. Remove three Phillips screws on front of control unit. (Fig. 2,
Step. 1)
4. Place the control unit into the service position. Press slot on
back of control unit into the horizontal sheet metal on the
bottom of the heater. (Fig. 2, Step. 2, pos. 1 & 2).
Figure 1
Checking the temperature sensors
1. Locate the cold water sensor immersed in the top of the water
valve (Fig. 3, pos. 1) and the hot water sensor on the hot water
outlet pipe (Fig. 3, pos. 2).
2. Using a thermometer, measure incoming cold water temperature
to the water heater. This can be done by opening the nearest
hot water faucet and letting the water fl ow for 3-5 minutes. With
the heater turned off, incoming cold water will pass through the
appliance and can be measured at this faucet.
Step 2 Step 2
Figure 2
Step 2 Step 2