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4
Function tests
4.1
General
This section describes the tests conducted on the heater
when it is installed and not installed to verify that it is in
working order.
WARNING
The heater must not be operated in enclosed areas such as
garages and workshops without an emissions extraction sys-
tem.
4.2
Repair Shop Level Testing
4.2.1 Testing individual components
IMPORTANT
For function tests always break the connection between the
control unit and the component you wish to test.
4.2.1.1 Glowplug resistance test
The resistance test must be carried out with an ohmmeter
suitable for small resistance values or Webasto Thermo Test
Diagnosis.
A resistance test with a simple digital multimeter is too inac-
curate to find the precise values. A new glow plug can be
measured to act as a reference.
The glow plug should have the following values in the test:
Glow plug:
Resistance at 25 °C:
Test current:
4.2.1.2 Air temperature sensor resistance test
If you conduct this test with a digital multimeter the air tem-
perature sensor must have the values shown in the follow-
ing diagram:
Temperature in °C
Characteristic resistance values of a PT 2000 overheating
sensor within a temperature range of 10 °C to 30 °C.
NOTE
12 V (red)
0.190 ... 0.250 Ω
< 5 mA
4.2.1.3 Water temperature sensor resistance test
A:
Resistance in kΩ
B:
Temperature of water temperature sensor -G18- in °C
C:
Resistance as a function of temperature
Table 401: Technical data water temperature sensor
Resistance
Temperature
nominal
[°C]
[Ohm]
-10
14.939,00
-5
11.425,00
0
8.816,00
5
6.855,00
10
5.373,00
15
4.241,00
20
3.372,00
25
2.700,00
30
2.175,00
35
1.763,00
40
1.438,00
45
1.180,00
50
972,80
55
806,30
60
671,80
65
562,40
70
473,00
75
400,00
80
339,70
85
289,50
90
247,80
4 Function tests
Resistance
Resistance
min.
max.
[Ohm]
[Ohm]
14.351,00
15.528,00
10.991,00
11.859,00
8.493,00
9.138,00
6.613,00
7.097,00
5.190,00
5.556,00
4.102,00
4.379,00
3.266,00
3.479,00
2.619,00
2.781,00
2.107,00
2.244,00
1.706,00
1.821,00
1.390,00
1.487,00
1.139,00
1.220,00
938,10
1.008,00
776,80
835,80
646,60
697,00
540,80
584,00
454,50
491,60
383,90
416,00
325,80
353,60
277,50
301,60
237,30
258,30
401
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