Technical data

Thermo 90 S / Thermo 90 ST Circuit diagrams
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10.3. Thermo 90 ST circuit diagram legend
Item Designation Comment
A1 Heater
A2 Control module
B1 Flame sensor
B2 Temperature sensor
B3 Temperature limiter/
Overheating guard
B4 Room thermostat
E Glow plug
F1 Fuse 20 A Flat fuse SAE J 1284
F2 Fuse 5 A Flat fuse SAE J 1284
F3 Fuse 20 A Flat fuse SAE J 1284
H1 “Heating” symbol in the display Operating indicator (in item P2)
H2 Light max. 2 W Operating indicator (in item S4)
H3 Symbol light Light (in item P2)
H5 Lamp, min. 1.2 W Switch-on indicator pumping
device
H6 Red LED Immediate heat button light,
ready indicator, switch-on
control (in item P2)
K3 Relay Circulating pump remote control
K5 Relay for vehicle fan
M1 Motor Combustion air fan
M2 Motor Circulating pump
M3 Motor Vehicle fan
P2 Digital timer For programmed operation
S4 Switch ON/OFF
Item Designation Comment
S5 1 or 2-pin disconnecting switch Emergency off switch, electric or
pneumatic
S7 Pumping device switch to positive
S8 Momentary-contact switch Immediate heat button remote
control
S9 Switch Heating/Circulating pump
remote control
S10 Switch Battery switch in positive
X1 Plug connector, 4-pin to item A2
X2 Plug connector, 2-pin to item A2
X3 Plug connector, 2-pin to item A2
X4 Plug connector, 2-pin to item A2
X5 Plug connector, 2-pin to item A2
X6 Plug connector, 2-pin to item A2
X7 Plug connector, 2-pin to item A2
X8 12-pin plug connection To item A2 (ST 2)
X9 12-pin plug connection to item P2
X10 Plug connector, 2-pin W-Bus diagnostic
X11 Plug connector, 2-pin to Y1
Y1 Metering pump Fuel pump for heater
Y2 Solenoid valve for pumping device