Theory Of Operation; 3-Port Module - Western HTS Mechanic's Manual

THEORY OF OPERATION

SNOWPLOW HYDRAULICS
The HTS™ snowplow hydraulic
system performs four blade
movements.
All movements require the vehicle
ignition (key) switch to be in the
"ON" or "Accessory" position and
the power to be activated on the
snowplow cab control.
Three of the four hydraulic
movements require energizing
the electric motor and appropriate
solenoid cartridge valves. The fourth
function, LOWER, does not energize
the motor but requires activating a
cartridge valve.
Power from the vehicle battery
is supplied to the solenoid coils
and the snowplow control via the
isolation module. The solenoid
cartridge valves operate in various
combinations, directed by the cab
control, to send hydraulic fl uid to the
snowplow lift and angle rams and/or
back to the reservoir.
BLADE
RAISE LOWER
MOVEMENT
Lit. No. 41467, Rev. 01
3-PORT MODULE ELECTRICAL
Overview
The isolation module acts as an
electrical hub, automatically directing
vehicle power to the appropriate
vehicle or snowplow lighting devices,
while also supplying battery power to
the snowplow control.
The vehicle high and low beams
enter and exit the isolation module
through positions B (left-side lighting)
and position C (right-side lighting).
Park, turn, and DRL signals also
enter through positions B and C.
The output of the vehicle high beam/
low beam select switch is directed to
the isolation module via the plug-in
harness. When the snowplow is not
attached to the vehicle, the signal
passes through the normally closed
relay contacts to the vehicle headlamps.
During this time, the isolation module
is inactive, placing no current draw on
the vehicle's electrical system.
ANGLE ANGLE
RIGHT LEFT
With the snowplow attached, the
isolation module is still inactive until
either of the two following conditions
are met: the vehicle parking lights
are turned ON or the vehicle ignition
switch is turned ON.
Turning ON the vehicle parking
lights activates a series of relays,
automatically transferring the vehicle
high and low beams to the snowplow
while supplying battery power directly
to the snowplow parking lights. All
snowplow lighting exits the isolation
module through position A.
Turning on the vehicle ignition switch
energizes a snowplow control relay,
supplying vehicle battery power
directly to the control via the vehicle
control harness and plug-in harness.
The vehicle ignition switch also
supplies power to the vehicle turn
signals. Activating the vehicle turn
signals energizes the turn signal
circuit, which supplies vehicle battery
power directly to the snowplow turn
signals.
Snowplow Daytime Running
Lamps
Because Daytime Running Lamps
(DRLs) are controlled diff erently on
some vehicles, two isolation modules
have been developed.
The standard isolation module
transfers the DRL output from the
vehicle headlamps to the snowplow
headlamps when the vehicle
ignition switch is turned ON and the
snowplow is attached.
The second isolation module,
designed for vehicles with dedicated
DRL bulbs, senses the vehicle in the
DRL mode and a series of relays
energize, placing the snowplow
low beams in series. This isolation
module does not turn OFF the
vehicle's dedicated DRLs.
April 15, 2021
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