Webasto Thermo Top V Workshop Manual - Thermo Top V
Thermo Top V
Description of operation
301
3
Description of operation
3.1
Switching on/starting process
The heater start-up can be carried out for the additional
heater via a remote control element, the immediate heat
button or timer programming of the clock.
For the auxiliary heater, the start-up is triggered by the pres-
ence of previously specified switch-on conditions (generally
from an outside temperature below 5 °C) via the vehicle
data bus.
Depending on the coolant temperature (and the engine
temperature, if provided for), the control unit decides which
start-up process is selected. Start-up processes are identical
with regard to the sequence, however differ in the length of
the individual phases (preheating, fuel delivery, etc.).
Fig. 301 Start-up process for Thermo Top V
After the heater has been switched on, the glow plug and
the combustion air fan are put into operation. Then the
metering pump is connected and the heater is run up to
approximately full load in a ramp. During this start-up
phase, it is checked whether a flame has formed with the
glow plug via a output measurement.
After full load is reached, the glow plug assumes the func-
tion of the flame monitor and checks the flame.
If no flame is formed or a flame out occurs, then a repeat
start-up is initiated depending on the amount of fuel deliv-
ered. If once again no flame is formed, the fuel delivery is
finished and a fault lock-out with run-on of the combustion
air fan is carried out. The heater can then only be put into
operation again as described in Paragraph 3.3.
If a flame out occurs during normal combustion operation,
a restart is automatically initiated.
3.2
Heating mode
Depending on the customer-specific requirements, the
heater switches into the energy-saving partial load mode
after reaching a certain temperature (approx. 80 °C). If the
temperature of the cooling liquid continues to drop due to
an increased heat requirement during partial load opera-
tion, then the heater switches over to full load operation
again. If the temperature continues to increase, the heater
switches into the control break from a pre determined tem-
perature (approx. 90 °C).
After the coolant has cooled down (to approx. 75 °C), the
heater restarts in the full load or partial load mode. If the
temperature rises to a defined switching temperature again,
the heater switches into the partial load mode or control
break again.
The temperature of the switching points is programmed in
the control unit for the specific vehicle. In isolated cases, the
control temperatures may have been set so that no partial
load mode takes place.
3.3
Restarting after fault lock-out
If a fault occurs, the heater switches into the fault lock-out
mode. After eliminating the fault cause, the heater can be
restarted by switching it off and then on again.
This does not apply after overheating or if a fault occurs sev-
eral times (generally 3x) without intermediate combustion
operation.
In case of a heater lock-out, the fault must be identified with
the Webasto Thermo Test PC diagnosis, the fault memory
must be printed out and the faults must be deleted. Then
the cause of the fault must be eliminated. Before starting
the heater, the heater lock-out must be released by remov-
ing the 20 A fuse as described below (also see Fig. 302).
Glow plug output
Fan
Metering pump
Fuel preheating
capacity
0) Heater On
1) Fan motor operating check
2) Checking resistance of glow plug/flame monitor
3) Preheating of glow plug
4) Selection of start-up process 7 to 9 via coolant temperature
(Start 6: warm start, Start 4 control break start)
5) Glowing of glow plug with resistance control
6) Fuel delivery (Phase 1 to 6 at full load)
7) Switching off of glow plug (glow plug ramp)
8) Flame-monitor measuring phase
9) Combustion operation at full load (5 kW)
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