Accessory lights on bed light switch

TSchevy · January 20, 2020

Has anyone added additional lights to the factory bed light switch? I’d like to add some lights on the rear bumper, and would like them on the bed light switch.

I searched around, but was unable to find a related post. If this has already been discussed, kindly point me in the right direction.

Lnafree · January 20, 2020

55 minutes ago, TSchevy said:

Has anyone added additional lights to the factory bed light switch? I’d like to add some lights on the rear bumper, and would like them on the bed light switch.

I searched around, but was unable to find a related post. If this has already been discussed, kindly point me in the right direction.

I was considering doing the same thing.

Smoothbassman · January 20, 2020

Yep,

Already did this. I added led lights under the bed rails so I could see what's in there at night under my tonnue cover. I tied into the bed light switch. You can use the same method to run any other lights you want back there.

Its a simple process, but you will need to use a relay to do it as the BCM looks for a specific voltage on that circuit. Adding more current draw on that circuit causes the bed lights to shut off after 3 seconds.

So I tapped into the bed light as the relay trigger. (top right of photo with the T-Tap) and pulled power from the trailer hitch circuit to run the additional LED lights in the bed. Installed the fused relay right to the body behind the tail lights (bottom of photo) so it would stay dry.

Works well with no issues in 6000 miles of running this truck.

TSchevy · January 21, 2020

18 hours ago, Smoothbassman said:

Yep,

Already did this. I added led lights under the bed rails so I could see what's in there at night under my tonnue cover. I tied into the bed light switch. You can use the same method to run any other lights you want back there.

Its a simple process, but you will need to use a relay to do it as the BCM looks for a specific voltage on that circuit. Adding more current draw on that circuit causes the bed lights to shut off after 3 seconds.

So I tapped into the bed light as the relay trigger. (top right of photo with the T-Tap) and pulled power from the trailer hitch circuit to run the additional LED lights in the bed. Installed the fused relay right to the body behind the tail lights (bottom of photo) so it would stay dry.

Works well with no issues in 6000 miles of running this truck.

That looks super clean! Do you happen to have a wiring schematic I could use? I was hoping the trailer circuit was adequate for power.

I have done simple light installs in the past, but all have been separate switch and fuse. Tapping into the current circuitry will be a somewhat new experience.

kaveman2769 · July 25, 2021

Please share the wiring setup, I installed the 3 piece led strip lights and tapped into the bed light and yes 3 seconds and out. Please share what relay you used.

thanks in advance

Lavear · November 28, 2021

Anyone ever get a wording diagram for this ?

Dave Schleier · November 29, 2021

30: hi current 12 volt, install a fuse inline (from battery or trailer plug)

87a: 12volt switched sent to lights being added

86: low current signal voltage (taken from 12volt supply to bed light)

85: frame ground

87: not used

30 power from

GETGONE · November 29, 2021

Looks like the post got cut off on what to hook where. I added the GM light kit for my multi-flex tailgate as well as swapped the lights to brighter aftermarket LED units. I added some 2"x2" LED cubes I had purchased for my Avalanche but never used. The current draw tripped the BCM and they would blink 3 times then go off. I also hooked the cube lights up to the reverse signal so they come on in reverse and at night when the approach lights turn on when you unlock the truck or lock it and leave. I had added a Curt 5th wheel wiring harness expecting I could get my signals from there for what I was originally wanting to do. I found on here that only the 12V+ wire has signal at all times. I pulled the tail light and looked at the wiring. I have LED bed lights in the corners from factory. I tapped that wire on the passenger side(or could use drivers side) and ran that to the 86 wire on a waterproof relay. I added a diode to it so current can't back feed to the bed light circuit. I also tapped the reverse light on the same side, added another diode here so current can't back feed the circuit and added it to the 86 wire. There is a harness that plugs in under the bed and connects to the tail lights. I purchased a new harness to keep as a spare in case I ever had electrical issues that required me to take it to the dealer. I can unplug everything I added and return it to stock. 30 wire I connected to the 12V of the Curt 5th wheel harness I added. This plugs in via T to the factory trailer plug. I have the actual 7 wire plug running into the blank in the passenger bed side where the 120V outlet would be if I had that option. 85 wire can be tapped into the trailer harness ground wire or find a suitable ground wire elsewhere on the chassis or trail light harness. 87 connects to your additional lights. I didn't add a fuse to mine since I'm using the 12V+ from the trailer harness and it is already fused. 87a is NOT used and can be removed or taped off. I heat shrunk/electrical taped up connections and then zip tied the relay to the Curt 5th wheel harness along the tail panel of the bed.

For those not wanting to read it all:

Waterproof relay(as shown above)

30 wire - 12V+ from trailer wire circuit

85 wire - 12V- ground to trailer wire ground, taillight ground, or other suitable chassis ground

86 wire - 12V+ input from LED bed lights and/or reverse lights, using a diode on each input wire to prevent back feeding trigger circuit

87 wire - 12V+ to your additional lights

87a wire - NOT used and can be removed from relay harness or taped off. Not all relays have this pin/wire

RedLT · January 4, 2022

On 11/28/2021 at 9:16 PM, GETGONE said:

Looks like the post got cut off on what to hook where. I added the GM light kit for my multi-flex tailgate as well as swapped the lights to brighter aftermarket LED units. I added some 2"x2" LED cubes I had purchased for my Avalanche but never used. The current draw tripped the BCM and they would blink 3 times then go off. I also hooked the cube lights up to the reverse signal so they come on in reverse and at night when the approach lights turn on when you unlock the truck or lock it and leave. I had added a Curt 5th wheel wiring harness expecting I could get my signals from there for what I was originally wanting to do. I found on here that only the 12V+ wire has signal at all times. I pulled the tail light and looked at the wiring. I have LED bed lights in the corners from factory. I tapped that wire on the passenger side(or could use drivers side) and ran that to the 86 wire on a waterproof relay. I added a diode to it so current can't back feed to the bed light circuit. I also tapped the reverse light on the same side, added another diode here so current can't back feed the circuit and added it to the 86 wire. There is a harness that plugs in under the bed and connects to the tail lights. I purchased a new harness to keep as a spare in case I ever had electrical issues that required me to take it to the dealer. I can unplug everything I added and return it to stock. 30 wire I connected to the 12V of the Curt 5th wheel harness I added. This plugs in via T to the factory trailer plug. I have the actual 7 wire plug running into the blank in the passenger bed side where the 120V outlet would be if I had that option. 85 wire can be tapped into the trailer harness ground wire or find a suitable ground wire elsewhere on the chassis or trail light harness. 87 connects to your additional lights. I didn't add a fuse to mine since I'm using the 12V+ from the trailer harness and it is already fused. 87a is NOT used and can be removed or taped off. I heat shrunk/electrical taped up connections and then zip tied the relay to the Curt 5th wheel harness along the tail panel of the bed.

For those not wanting to read it all:

Waterproof relay(as shown above)

30 wire - 12V+ from trailer wire circuit

85 wire - 12V- ground to trailer wire ground, taillight ground, or other suitable chassis ground

86 wire - 12V+ input from LED bed lights and/or reverse lights, using a diode on each input wire to prevent back feeding trigger circuit

87 wire - 12V+ to your additional lights

87a wire - NOT used and can be removed from relay harness or taped off. Not all relays have this pin/wire

That's good detailed information, thanks.

kmeleon · January 5, 2022

On 1/20/2020 at 4:26 AM, Smoothbassman said:

Yep,

Already did this. I added led lights under the bed rails so I could see what's in there at night under my tonnue cover. I tied into the bed light switch. You can use the same method to run any other lights you want back there.

Its a simple process, but you will need to use a relay to do it as the BCM looks for a specific voltage on that circuit. Adding more current draw on that circuit causes the bed lights to shut off after 3 seconds.

So I tapped into the bed light as the relay trigger. (top right of photo with the T-Tap) and pulled power from the trailer hitch circuit to run the additional LED lights in the bed. Installed the fused relay right to the body behind the tail lights (bottom of photo) so it would stay dry.

Works well with no issues in 6000 miles of running this truck.

Could you post a pic at night with the latest lluminated?

ScruffyZ71 · February 12, 2023

Is there no way to make BCM accept the added draw from the LED strips?

GETGONE · February 12, 2023

1 hour ago, ScruffyZ71 said:

Is there no way to make BCM accept the added draw from the LED strips?

No

DHBWA · March 7, 2023

I tapped the trailer 12v circuit and added a door type switch as I didn’t want to have to use the FOB to turn on the added lights. Tailgate drops, lights come on.

DHBWA · March 12, 2023

Only downside is the lights stay on all the time the tailgate is down. For any reason….No biggie to me but it could be to others…

GETGONE · March 13, 2023

2 hours ago, DHBWA said:

Only downside is the lights stay on all the time the tailgate is down. For any reason….No biggie to me but it could be to others…

Use a toggle switch instead.