Lit. No. 41298, Rev. 01 February 15, 2019
30
THEORY OF OPERATION
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.
3-PORT MODULE ELECTRICAL
• 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.
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