Thermo King UT-1200, Manual

Page: 82 / 169

Electrical Maintenance
82
Base Controller LEDs
The base controller has LEDs that indicate which
outputs are energized. The LED is illuminated
when the associated circuit output is energized.
Smart FETs
A Smart FET (Field Effect Transistor) is a self
protecting output device used for the functions
shown in the table below. If an over-current
condition occurs, the Smart FET will turn off until
the over-current condition no longer exists. It will
then resume normal operation. A fuse is not
required. Smart FETs are not field repairable.
Refer to the appropriate Microprocessor
Diagnostic Manual for more information about
the Smart FETs.
Not all Smart FETs shown below are used on
single temperature truck units.
SMART REEFER 3 (SR-3)
Microprocessor Controller
Refer to the SR-3 Truck Single Temp Diagnostic
Manual TK 55208 for complete service
information about the Microprocessor Controller
and the related components.
Flywheel (RPM) Sensor
The flywheel (RPM) sensor is mounted on the
engine starter mounting flange adjacent to, but not
touching, the flywheel (backed off 1/4 turn).
The flywheel sensor is a device containing an
inductance coil and magnet. When the magnetic
field is distorted by the passing ring gear teeth, the
inductance coil generates an AC electrical signal
that has a voltage and frequency variation
proportional to the engine RPM.
By monitoring the frequency of this signal, the
controller can monitor the engine speed and
precisely control the timing of the starter
disengagement.
If the flywheel sensor fails, the starter may not
disengage or engage properly and a fault code will
be generated.
Interface Board LED Functions
LED # Function
LED 3 K2 Preheat Circuit
LED 4 K4 Damper Circuit
LED 5 K3 High Speed Circuit
LED 6 K1 Run Relay Circuit
LED 7 K5 Diesel/Electric Relay
LED 8 Condenser Inlet Solenoid (CIS) Circuit
LED 9 Receiver Tank Pressure Solenoid
Solenoid (RTPS) Circuit (Not Used)
LED 10 Hot Gas Solenoid (HGS) Circuit
LED 11 Purge Valve (PV) Circuit
LED 17 (Not Used)
LED 18 Alternator Excite
LED 19 Liquid Injection Solenoid (LIQ) Circuit
LED 20 (Not Used)
LED 21 Status – Flashes once per second when
the base controller is powered and
operating normally. Flashes several times
per second when flash loading. Is on
without flashing during reboot and when
base controller under test. Flashes twice
within 1 second followed by 1 second off if
a CAN communication error is present.
LED 22 K8 Drain Tube Heaters Remote
Evaporator (Not Used)
LED 23 K9 On/Off Circuit
LED 24 K6 Fuel Solenoid Pull-In Circuit
LED 25 K7 Starter Circuit
LED 26 (Not Used)
LED 27 ETV – D*
LED 28 ETV – B*
LED 29 ETV – A*
LED 30 ETV – C*
* Illuminated when the respective ETV output is
energized. On applications without an ETV the ETV
LED's may be illuminated even though there is no
ETV present.
Base Controller Outputs With Smart FETs
Output Function
EVA, EVB, EVC, EVD ETV Outputs
CIS Condenser Inlet Solenoid
HG Hot Gas Solenoid
PV Purge Valve
LIQ Liquid Injection Solenoid
EXC Alternator Excite
LV1 Not Currently Used
LV3 Not Currently Used
LLSP Not Currently Used