Thermo Pro 90
6 Function checks
603
6.4
Testing individual components
6.4.1 Checking resistance of the coolant
temperature sensor
When testing with a digital multimeter, the temperature sen-
sor should show the following values:
Resistance at 25 °C: 990
to
1010 Ohm
Test current:
< 1 mA
6.4.2 Checking resistance of the glow plug
When testing with a digital multimeter, the glow plug should
show the following values:
6.4.3 Checking resistance of the exhaust gas
temperature sensor
When testing with a digital multimeter, the exhaust gas tem-
perature sensor should show the following values:
Resistance at 25 °C: 2195 ± 4 Ohm
Test current:
< 5 mA
6.4.4 Checking the combustion air fan
The combustion air fan speed must be checked in the permis-
sible operating voltage range. Check for scraping noise.
NOTE
The combustion air fan is always checked in installed state, i.e.
the control unit must be mounted on the fan housing. This is
due to the sensors in the control unit that are required for
speed control.
The test is performed with the Webasto Thermo Test PC diag-
nostics.
Specified speed 5500 rpm
Listen for grinding noise and start-up noise. Start up to the
specified speed must be heard. The error message "Fan motor
stiff" must not be activated.
6.4.5 Checking the DP42 fuel pump
ATTENTION
•
The fuel pump must not be operated with the operating
voltage (12 or 24 ).
•
Power must not be supplied to the pump when a control
unit is connected.
When testing with a digital multimeter, the DP42 should show
the following values:
Resistance at 25 °C:
4.95 to 5.45 Ohm
Test current:
< 1 mA
Diesel delivery rate:
See “Technische Daten” on Page 401.
6.4.6 Checking the overheating protection
NOTE
The overheating protection should only be removed when it is
to be renewed. It must be checked in installed state.
Check continuity of overheating protection at room tempera-
ture, the electrical resistance must go towards 0 ohm.
6.4.7 Checking the U4840 coolant pump
The coolant pump should be checked with the component
test function in Webasto Thermo Test PC diagnostics. The
coolant pump can also be checked by touching it with your
hand. Constant vibration of the coolant pump should be felt.
Technical data :
Glow plug:
12 Volt (red)
24 Volt (green)
Resistance at
25 °C:
270 ± 35 mOhm
770 ± 100 mOhm
