Western HTS Mechanic's Manual page 34

THEORY OF OPERATION
3-PORT MODULE ELECTRICAL
Green Label DRL Module
(PN 29070-1)
Snowplow not attached to vehicle:
System is inactive. Vehicle lighting
system functions normally. Reason:
No ground to module.
Snowplow attached to vehicle:
System is inactive until either the
switched accessory wire or the
vehicle parking lights are activated.
Vehicle and snowplow lighting
systems function as outlined in the
Theory of Operation Overview.
Reason: ground path is established
from battery common to pin C on
port A of the 3-port module via the
following harnesses: vehicle battery
cable, vehicle control harness,
adapter, plug-in harness, vehicle
lighting harness and snowplow
lighting harness.
Lit. No. 41467, Rev. 01
• Activating a switched accessory
wire (a key-controlled power
source) applies battery voltage to
the VACC input of the module. A
control circuit senses the voltage
and energizes the coil of the
control power relay (part of the
3-port module). Energizing the
coil of the control power relay
causes the relay contacts to shift
from the "N.O." (normally opened)
position to the "N.C." (normally
closed) position, which supplies
battery voltage to the snowplow
control via the plug-in harness
and the vehicle control harness.
The switched accessory wire only
controls battery voltage to the
snowplow control.
• Activating the vehicle park
light circuit applies voltage to
the module park circuit input. A
control circuit senses the voltage
and turns ON a solid state power
device, which applies battery
voltage to the snowplow park
lamp fi laments via the vehicle and
snowplow lighting harnesses.
• With the park light circuit
energized, the control circuit
monitors the vehicle high
and low beam inputs. When
battery voltage is sensed, the
appropriate solid state power
devices are turned ON, supplying
battery voltage to the snowplow
headlamps via the vehicle and
snowplow lighting harnesses.
Toggling the dimmer switch
between high and low beam will
toggle the snowplow high and
low beams.
• Activating the turn signal applies
voltage to the module turn signal
circuit input. A control circuit
senses the voltage and turns
ON a solid state power device,
which applies battery voltage to
the snowplow turn signal lamp
fi laments via the vehicle and
snowplow lighting harnesses.
• PN 29070-1 Only: On vehicles
equipped with DRLs integrated
into the vehicle headlamps.
Activation of the switched
accessory wire (a key-controlled
power source) port C, position C,
applies battery voltage to the
module's high and low beam
relay coils, which causes the
relay contacts to shift from the
"vehicle" to the "snowplow"
position. This module will
transfer the vehicle headlamp
DRLs to the snowplow (turns
off vehicle DRLs).
• On vehicles equipped with
dedicated DRL bulbs or
vehicles using the turn signals
as DRLs, this module will not
turn OFF the vehicle bulbs.
While the vehicle is in the
DRL mode, this module will
illuminate the snowplow light
turn signal fi laments.
April 15, 2021
34