3 Functional description
Thermo Pro 90
301
3
Functional description
3.1
Switching on and residual heat utilization
Switching on the heater
The heater is switched on with the control element.
Activation of residual heat utilization
Every time it is switched on, the heater checks the coolant
temperature before the heating process. Residual heat utiliza-
tion is activated automatically at coolant temperature above
60 °C. When residual heat utilization is activated, the coolant
pump for the heater and the vehicle blower are automatically
actuated.
Residual heat utilization can only be activated from the "OFF"
state, i.e. the "residual heat utilization" state is not assumed
from the "fault lock-out", "ADR lock-out" and "heater lock-
out" states.
Deactivation of residual heat utilization
Conditions for deactivating residual heat utilization:
a) When the lower operating voltage limit has been
exceeded
b) When the coolant outlet temperature is lower than 60 °C
c)
When the heater is switched off
Fig. 301 Thermo Pro 90 functional sequence
Glow plug
Fuel pump
Combustion air fan
Exhaust gas tempe-
rature sensor
Operation indicator
lamp
U4840 coolant pump
Vehicle blower
Afterrunning finished
Preheating 15 to 20 s
Fuel pump / partial load (1/4)
"Flame ON" detection
Stabilization time
Coolant temperature dropped
Full load
Switching off (afterrunning period)
"Flame OFF" detection
Afterrunning finished
12
13
14
15
16
17
18
19
20
21
Switching on
Heater
Preheating 40 s
Fuel pump / partial load (1/4)
"Flame ON" detection
Stabilization time
Full load
Vehicle blower "On"
Control range
Normal shutdown pause
"Flame OFF" detection
1
2
3
4
5
6
7
8
9
10
11
Possible coded control temperatures
