Group 30 Electrical System—VNL, VNM
Design and Function
Cab Marker LED Lights (With Sunvisor)
When the sunvisor option is installed, the cab marker
lights are sealed LED units. When replacing, the entire
LED unit must be replaced. Cab marker lights without the
sunvisor option are standard bulbs (see
Bulb Replace-
ment List in this manual).
W3001004
Daytime Running Lights
Daytime running lights (DRL) turn the low beam head-
lamps on, with reduced voltage, whenever the ignition is
on and the parking brake is released. The DRLs will come
on even though the headlight switch is off. The DRL mod-
ule is located inside the cab, under the relay panel.
The DRL module reduces the voltage to the headlamps
by using pulse width modulation to “pulse” the low beams
on and off at a rate of 70 Hz (which is faster than the
eye can detect). The reduction in voltage is about 24%
RMS of the applied voltage. If the applied voltage is 13.8
VDC, a DC voltmeter such as a Fluke 87 will show the
average voltage between 7.5 and 8.5 VDC. The left and
right headlamps are controlled separately.
Operating voltage
10-19 VDC
Under voltage shutdown
9.5 VDC
Over voltage shutdown
19.5 VDC
Short circuit shutdown current
50 A
Daytime Running Lights Module
Pin
Circuit
No.
Description
A
40
12V supply
B
44L/32L
LHS 9V (Low Beam)
Output
C
44R/32R
RHS 9V (Low Beam)
Output
D
42
Parking Brake Disable
E
0H
Ground
F
41
Ignition Input
G
Not used
H
Not used
W3000555
36
