Chapter 6 Control system diagram
198 SMSO-2-02.06- 15.07.03
6.5.14 Temperature sensor “coffee”
36V
5V DC
36V S L1, N
Operating condition
When the machine is switched on the temperature sensor measures the temperature in the “coffee” instant heater.
Symptoms
“Temp. sensor coffee” is displayed.
Procedure
Service technicians are not able to test the temperature sensor with a sufficient degree of accuracy. Therefore, if you suspect
that the temperature sensor is malfunctioning, you should replace it. Check for calcium deposits: dismantle and decalcify if
necessary. After a safety thermostat has been triggered, the temperature sensor must be replaced!
Process
step
Check Possible cause Remedy
1
Take voltage measurement at
plug X 8 2 on unit control system:
5 V DC ?
Check the voltage supply (see
“Power PCB, control voltage”)
Voltage supply failure / faulty
2
Voltage measurement at tempera-
ture sensor plug
Input, 5V+ = 5 V DC ?
Output, 5V+ < 5 V DC ?
(at 20
o
C)
Plug contacts on unit control sys-
tem faulty / oxidised
Cable broken or pulled out of plug
Plug-in connection to temperature
sensor faulty/oxidised
Check / replace plug contacts
Replace cable
Replace temperature sensor
Resistance measurement at temperature sensor plug
Switch off voltage
Loosen the cable from the plug terminals
Disconnect the plug-in connection
3
Measure resistance at temperature
sensor; nominal resistance:
(depends on temperature)
12.5 kΩ ? (at 20
o
C)
10.0 kΩ ? (at 25
o
C)
(if you suspect that the tempera-
ture sensor is malfunctioning, you
should replace it.)
Faulty temperature sensor
Cable to temperature sensor
broken (loose contact) or pulled
out of sealed union nut
Replace temperature sensor
Reconnect the temperature sen-
sor plug.
Restart the machine
If the “temp. sensor coffee” mes-
sage continues to display:
Cable to X8 1 faulty
Faulty unit control system
Replace cable
Replace unit control system
NO
YES
NO
YES
NO
ES
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