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07 Gmt-900 Aux. Light Changes

Well GM changed the deal with the new 07s VYU plow prep beacon
light wiring and switch location.

The light switch is now on the ceiling (instead of the dash) mounted on
the overhead "console". The wire colors have changed and are now
dark green+ and black-.
According to the owners manual they are blunt cut and laying above
the overhead "console".

I am gonna get brave (again) and drop the overhead console and look
to see if the wires are there. If so I am gonna fish them out and run
them out the side of the headliner and out the door for my beacon.

I wonder if you need to install a Maxi fuse underhood (stud 2???)
like the GMT-800s..................

Will post when I do the deed !!!!!!!!!.............geo
 

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Electrical Manual – 2007 Light Duty – “NEW” Full Size C/K Pickup A-14
PAGE
Snowplow Prep Package (VYU) Electrical Provisions
Emergency Roof-Mounted Lamp Switch
This provision includes an over head console mounted switch , a relay,
and wiring which terminates at the roof as coiled blunt cut wires – Option
TRW. There are two blunt cut 12-gauge (3.0 mm2) wires, one is Dark
Green (roof-mounted lamp power), it is controlled by the over head
console -mounted switch through the relay, the other is Black (ground).
The Dark Green power wire is protected by the 30-Amp S/ROOF fuse
#33 which is located in the Underhood Electrical Center.
VYU Generators
• On 1500/2500 Series trucks equipped with Gas Engines, the VYU
option provides upgrade to a larger 160 amp output generator
• On 2500/3500 Series trucks equipped with Diesel Engines, the VYU
option provides upgrade to dual 125 amp generators
• Refer to the Generator Chart on page A-18
Accessory Harness Grommet
Trucks will come equipped with a predrilled 42mm pass-through hole
located on the dash panel on the left hand side of the vehicle. The hole
will be sealed with a grommet (see Figure 3) which can be used by the
upfitter for pass-through wiring. To use the grommet (part# 15336702),
the upfitter slices off the tape tab end (in engine compartment) of the
grommet and then spreads it open to pass wiring through.
Forward Lamp Harness In-Line Connectors
The turn signals are driven from the BCM. Changes in turn signal current
may require the use of additional relays. The Studs on the UBEC can be
used for battery power for the relays. This wire requires a separate
in-line fuse.
The Chevrolet (X88) and GMC (Z88) utilities have different forward lamps.
• Chevrolet forward lamp wiring harness will have a set of mating
eight cavity connectors on both the left and right hand side of the
vehicle The upfitter will be able to disconnect the in-line connectors
which will allow interfacing with the forward lamp circuits (Front
Parklamp, Turn Signal and DRL). The headlamp circuits may be
accessed from the headlamp connectors.
• GMC lamp wiring harness will have a set of mating 3 cavity
connectors on both the left and right hand side of the vehicle for
Turn Signal and Park Lamps. High and Low beams do not have an
in-line connector. The VYU options adds an additional set of mating
3 cavity connectors on both the left and right hand side of the
vehicle for High and Low beams.
The Chevrolet (X88) and GMC (Z88) pickups have the same forward lamps.
• These are similar to the Chevrolet utility. The difference is the utilities
have a separate Daytime Running Lamp (DRL). The Pickups use a
reduced intensity Low Beam Headlamp for DRL. Both the pickups
and the Chevrolet utility use the same eight cavity connectors for
the forward lamp wiring. The difference is the pickups have no
connection for the DRL.
Backup Lamp Power Feed
A backup lamp power feed is provided at the rear of the vehicle through
the trailer wiring harness as a standard feature. This circuit is protected
by the 10-Amp TRLR B/U fuse which is located in the Under hood
Electrical Center. On vehicles with Light Duty Trailer Wiring this circuit can
be accessed through the Light Green trailer wire. This wire is located in
pin A of the trailer connector at the rear of the vehicle (see figure 6). On
vehicles with Heavy Duty Trailer Wiring option, this connector is mated
with a socket at the rear of the vehicle (see figure 7).
 

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Battery power is supplied through a 30 amp fuse to a wiring harness located in the roof. Power is controlled with a switch located in the
overhead console. The customer or vehicle upfitter must complete the installation to an added accessory such as an emergency beacon lamp.
Maximum rated electrical load is 21 amps (250 watts). The added electrical requirements must not exceed 21 amps (250 watts). Running the
accessory for long periods of time with the engine off may run the battery down.
Installation Instructions — Emergency Vehicle Roof Panel Lamp
Wiring to the accessory can be done by either directly connecting the wire in the roof to the accessory (Option A) or by using Wiring Harness
Package part number 12150250 obtained from GM Service Parts (Option B).
Roof Mounted Beacon (TRW)
A. 25.39 inches (645 mm)
B. 17.32 inches (440 mm)
C. 3.94 inches (100 mm)
D. Roof Centerline
E. Roof Edge Emergency Vehicle Roof Panel Lamp (continued on next page)
 

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Roof Mounted Beacon (TRW) (cont'd)
Emergency Vehicle Roof Panel Lamp
(continued from previous page)
1. Disconnect the battery negative (-) cable at the battery.
2. Make the electrical connections using either option A or
option B.
Notice: Pulling the wiring harness through a panel hole that has
sharp edges may cause damage to the wire and/or wire
insulation. Remove sharp edges from the panel hole before
pulling the wire through it.
Option A: Roof Wires Directly to Accessory
1. Drill a 3/8 inch to 1/2 inch (10 to 13 mm) hole in the outer
roof panel in the area shown in the illustration. The hole should
only go through the outer panel. Remove all sharp edges from
the drilled hole.
2. Remove the inside overhead console access panel/lamp lenses.
3. The accessory harness is coil tied to the passenger’s side of the
vehicle at the console inner bracket.
4. Cut the tape holding the harness coil.
5. As one person watches the roof hole from the outside for the
end of the harness, a second person from the inside of the
vehicle should snake the harness toward the hole.
6. Pull out the wiring harness being careful to avoid scraping the
insulation on the edge of the hole.
7. Extend the wiring harness to the accessory.
8. Connect the dark green wire to the accessory hot terminal.
9. Connect the black wire to the accessory ground terminal.
10. Cover the hole in the roof with a durable sealant such as
silicone rubber sealer.
11. Reinstall the overhead console access panel/lamp lenses.
Option B: Use Wiring Harness Package 1215 025 0.
Obtain from GM Service Parts through the GM Dealership
1. Drill a 1.25 inch (32 mm) hole in the outer roof panel in the area
shown in the illustration. The hole should only go through the
outer panel. Remove all sharp edges from the drilled hole.
2. Remove the inside overhead console access panel/lamp lenses.
3. The accessory harness is coil tied to the passenger’s side of the
vehicle at the console inner bracket.
4. Cut the tape holding the harness coil.
5. As one person watches the roof hole from the outside for the end
of the harness, a second person from the inside of the vehicle
should snake the harness toward the hole.
6. Pull out the wiring harness being careful to avoid scraping the
insulation on the edge of the hole.
7. Cut the wire to length. Install terminals to wire ends and insert
into the connector. The brown wire goes to cavity A and the
black wire in cavity B. Push in the secondary lock to retain
the wires.
8. Attach the harness assembly from the package to the accessory.
Cover with the supplied conduit for added protection. Connect
the orange wire to the accessory hot terminal and the black wire
to the ground.
9. Complete the connection from the roof harness to the
extension harness. Cover the mated connector with the
supplied foam. Push the foam covered connection and
excess wire through the roof panel hole.
10. Reinstall the overhead console access panel/lamp lenses.
Emergency Vehicle Roof Panel Lamp (continued on next page)
 

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The auxiliary lamp switch is located on the overhead console.
This switch includes wiring provisions for a dealer or a qualified service center to install an auxiliary roof lamp. When the wiring is connected
to an auxiliary roof mounted lamp, pressing the bottom of the switch will activate the lamp and illuminate an indicator light at the bottom of the
switch. Pressing the top of the switch again will turn off the roof mounted lamp and indicator.
1. Be sure that the auxiliary lamp switch is off.
2. Reconnect the battery negative cable.
3. Turn the auxiliary lamp switch on. The accessory should now be working. If it is not working, check the connections.
4. After ensuring that the accessory is working properly, install the grommet in the hole. Seal with silicone sealer to prevent water leakage.
Notice: Overloading the vehicle’s electrical system may damage your vehicle’s accessories.
Do not overload the vehicle’s system by having unnecessary accessories on at the same time.
 

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Guys .........With your 07/08 GMT-900 aka the new new body style
If your wondering how to remove the little roof
console and light in the ceiling to get at the beacon light
wires with the VYU plow prep option. Heres a pic:
 

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Heres the rest of the GM bulletin for 07/08 GMT-900:
Remove the inside overhead console access panel/lamp lenses.
The accessory harness is coil tied to the passenger’s side of the
vehicle at the console inner bracket.


Callout

Component Name

1

Front Overhead Console Lens

2

Roof Console Screws (Qty: 2)

Notice: Refer to Fastener Notice in the Preface section.

Tighten
2 N·m (18 lb in)

3

Roof Console Assembly

Tip

Disconnect the electrical connectors.
If replacing roof console assembly, transfer all necessary components.
4

Roof Console Retainers (Qty: 2)

Tip
Pull down to disengage clips.

© 2008 General Motors Corporation. All rights reserved.
 

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BTW: Heres a pic of the 99 and up GMT-800 VYU beacon light
switch for those who haven't seen one:

Heres a close up pic:
 

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hello guys could you tell me if that wiring is in headliner on a 95 chevy. truck has vyu code but no switch on dash thanks ron
 

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No, this was for the newer trucks only. Your 95 doesn't have the harness or switch.

Really not an issue to wire your own switch though, if your using LED's you don't really need a relay either.
 

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JOSH...........The vents are on the outside back lower portion of the cab between the cab and the box. One on each side.
 

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GUYS............Just FYI if you have a 03 and up GM truck with the plow prep pkg. and the aux light switch on the dash.

If you happen to dig the wires out of the headliner and have NO power to them or the button on the dash don't light up either heres the EASY solution before you rip your hair out or waste time and money at the dealer...........

Check your underhood fuse center for stud #2 for a maxi fuse. Cheap GM stopped putting in a fuse around 03. Pop in a fuse and you will have power !!

Please note stud #1 will also be missing a fuse and that one controls the aux. power wire in your trailer hitch plug...................geo:D

BTW: the 2 wires your looking for in the headliner are a heavy brown+ and a heavy black-
and are blunt cut and just laying up there bare. I guess thats why NO fuse installed?????
NO POWER! I have a 2007 Chev 2500 WT It has the beacon switch on the dash, I found the loose wires in the headliner on the Drivers side. One heavy brown wire and slightly smaller gauge black wire taped together. Blunt cut but the ends were covered in grey electrical tape. Fished it out the 3rd brake light, but no power. Light beside the switch on the dash comes on when I press it. There is a 30A fuse installed (Was already there) in "stud 2" in the fuse box.
Any ideas???
 

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NO POWER! I have a 2007 Chev 2500 WT It has the beacon switch on the dash, I found the loose wires in the headliner on the Drivers side. One heavy brown wire and slightly smaller gauge black wire taped together. Blunt cut but the ends were covered in grey electrical tape. Fished it out the 3rd brake light, but no power. Light beside the switch on the dash comes on when I press it. There is a 30A fuse installed (Was already there) in "stud 2" in the fuse box.
Any ideas???
 
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