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4.14
Coolant temperature sensors
Fig. 14 Coolant temperature sensors
A Overheat sensor
B Coolant temperature sensor
The sensor values are used for the coolant temperature control
and for protecting the heater against overheating.
The sensors are connected to the control unit by the cabling.
4.15
Exhaust gas temperature sensor
Fig. 15 Exhaust gas temperature sensor attachment and connector
A Exhaust gas temperature sensor
connector
A sensor is installed on the exhaust gas stub of the heater to
monitor the temperature in the exhaust gas. The sensor is con-
nected to the control unit by the cabling.
4.16
Coolant pump
The standard variant of the Thermo Top Pro 120 | 150 are oper-
ated with the coolant pump U4850. The coolant pump is
switched on by the heater control unit.
If using a CPoff heater variant (see chapter 3.2.2, "Thermo Top
Pro 120 | 150 CPoff" on page 5), which can also be recognised
via the "CP OFF" label, then a coolant pump is controlled ex-
ternally. Exact specifications to this effect can be found at the
end of this chapter in the section "Use of an external coolant
pump".
9039412C Workshop manual TTP 120 _ 150
A
C
B
C Cover for sensors
A
B
B Exhaust gas temperature
sensor
C
Fig. 16 Coolant pump U4850
A Coolant pump U4850
B Coolant outlet
NOTE
The use of the U4850 coolant pump in military vehicles
or military applications is prohibited.
NOTE
The heater must be operated with a coolant pump.
Pumps that have been dropped must not be re-used.
Dropping may lead to external impact points and in-
ternal damage.
Possible cracks in the plastic part of the pump may lead
to a leakage in the pump compartment or the sur-
rounding area. This may result in operational failures of
the pump due to the ingress of coolant into the elec-
tronic area.
Characteristics of the coolant pump U4850
NOTE
Reactivation of the coolant pump motor:
The coolant pump motor can be reactivated from the
dry-running protection or sleep mode. This is done by
isolating the power supply for > for 2 min. After restor-
ing the power supply, the coolant pump motor starts in
soft-start again.
l Start-up
The coolant pump motor starts up within 2 seconds.
l Protection against blocking, running dry and overload
A continuous check of the coolant pump for blocking, run-
ning dry and overload is carried out during the start and
regular operation.
If such an error case is detected, the coolant pump sends a
corresponding diagnostic signal to the heater control unit
and automatically deactivates itself temporarily. The
coolant pump attempts to start again.
After 20 unsuccessful start attempts, the coolant pump
switches itself off. To carry out a renewed start attempt,
the coolant pump must be turned off and switched back on
again.
The coolant pump motor is not damaged by hydraulic over-
pressure of the coolant pump provided that the following
limits are observed:
– Max. overflow forwards: 2400 l/h
– Max. overflow backwards: 500 l/h
Description of the components | 4
C Coolant inlet
A
B
11 / 49
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