Installation manual

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Thermo 90 S / Thermo 90 ST Circuit Diagrams
12.2 Thermo 90 ST Circuit Diagram Legend
 Digital timer P2:
Connection X14 to Red jumper of switch harness results
in continuous operation with immediate heating
(recommended for trucks requiring sleeper heating)
Connection X14 to vehicle ignition connection results in
variable heating duration that can be programmed (10
min. to 120 min.); default setting 120 min. when ignition
key is switched off. (Recommended for School bus,
Coach and Transit vehicles.)
 Optional connection to vehicle instrumentation
panel lighting circuit.
The following Table applies to Figures 34 and 35.
Item Designation Comment
A1 Heater
A2 Control module
B1 Flame sensor
B2 Temperature sensor
B3 Temperature limiter/
Overheating guard
B4 Room thermostat
BT Battery Vehicle battery
DS Illuminated toggle Operating indicator (in item S1)
E Glow plug
F1 Fuse 10 A ATM mini flat fuse
F2 Fuse 5 A ATM mini flat fuse
F3 Fuse 20 A ATM mini flat fuse
F5 Fuse 30 A ATM mini flat fuse
H1 “Heating” symbol in the
display
Operating indicator (in item P2)
H3 Symbol light Light (in item P2)
H6 Red LED Immediate heat button light,
ready indicator, switch-on control
(in item P2)
K1 Relay Vehicle fan interface harness
option
M1 Motor Combustion air fan
M2 Motor Circulating pump
P2 Digital timer 1531 For programmed operation
S1 Toggle switch ON/OFF
X1 12-pin plug connection To item A1
X2 Plug connector, 2-pin To Y1
X3 9-pin plug connection To power / control harness
X4 Plug connector, 3-pin To optional blower interface
systems (Sleeper Pak™)
X5 5-pin relay socket Vehicle fan interface harness
option
X6 Plug connector, 2-pin Diagnostics
X7 8-pin plug connection To item X9
X8 1-pin plug connection
To item X9 - pin-10 (see
)
X9 12-pin plug connection To item P2
X11 12-pin plug connection To item A2 (ST 1)
X12 12-pin plug connection To item A2 (ST 2)
X13 Plug connector, 2-pin To item A2 (ST 3)
Y1 Metering pump Fuel pump for heater