Valeo Thermo AC 070, Workshop Manual

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401
Thermo AC/DC 4 Functions of the heater
4 Functions of the heater
4.1 General functional description of the
heater
In the fully electrical operated heater Thermo AC/DC the
coolant of the vehicle is heated by electric heating cart-
ridges.
Control elements to switch the heater on and off can be:
– Switches
– Relays
– Valeo preselection timer
To monitor the operation an operation indicator or the
Valeo preselection timer is to be provided.
The heating cartridges are switched by a load contactor.
The control voltage for the contactor is generated by an
AC/DC converter (integrated in the Thermo AC200/
DC200 in the heater).
On the vehicle side, the control circuit contains an opera-
ting element by means of which the heater is taken into
operation. On the heater side, a control thermostat and a
temperature limiter are integrated, which are attched to
the heater. In operation, they enable the heating cart-
ridges to be switched on automatically when a lower swit-
ching threshold is reached and their switching off when
the upper switching threshold is reached (regulating ther-
mostat) as well as a switching off of the heater in the event
of an overheating (temperature limiter).
Table 401 shows
the corresponding default values.
The heater must be protected and monitored on the
vehicle side by a ground fault interrupter (AC) respective
an insulation monitoring device.
Heating is only permitted with a sufficient coolant flow rate
(> 1500 l / h).
When the heater is switched off, ensure that the circula-
ting pump is still running 120sec.
Table 401 Standard switching thresholds
Standard
Lower switching threshold in °C 68
Upper switching threshold in °C 75
Overheating protection in °C 125