Troubleshooting Guide | AE12, RP12T, US12
| 3
Data subject to change without notice | Printed in the USA | BTC 721002308 A | 09.2013
Bosch Thermotechnology Corp.
Checking the Thermal Cut Out:
1. Locate the thermal cut out switch (see Fig. 3).
Figure 3
Reset button on Thermal Cut Out
2. Press the button located in the center of the cut out
switch. If you feel it click (similar to a ball point pen), then
the thermal cut out was tripped.
NOTICE:
The thermal cut out trips because of another underlying
problem, such as scale, low
fl
ow with warm inlet water,
high temperature setting or preheated water. It is
important to
fi
nd the issue before returning the heater to
service.
3. Document
your
fi
ndings in the Water Heater questionnaire
on page 6.
Step 4 – Checking continuity and resistance
Ensure the circuit breaker powering the appliance is still shut
off.
Check the thermal cut out switch for continuity.
1. Check for continuity between connections labeled A-B and
also C-D (see Fig. 4).
2. Document
your
fi
ndings in the Water Heater questionnaire
on page 6.
Figure 4
A
C
D
B
Check the
fl
ow switch for continuity.
1. With no water
fl
owing through the unit, check continuity
between the brown wire and the yellow wire on the circuit
board using 100 ohms scale (see Fig. 5). A stuck or dama-
ged
fl
ow switch will show a closed circuit without water
fl
ow causing the TCO to trip.
2. Now with water
fl
owing through the unit, check continuity
between the brown wire and the yellow wire on the circuit
board using 100 ohms scale (see Fig. 5).
Figure 5
3. Document
your
fi
ndings in the Water Heater questionnaire
on page 6.
