Led lights under vehicle when unlocking.

[sbarron]

I just did this on my truck. You want to tie into the dome light so the ground is lit by both the remote or opening any of your doors. It's really simple to do. You do not need a relay. I tried wiring one with the dome light as the trigger. The problem is that when using the remote to unlock the doors the voltage on the dome light isn't enough to fully activate the relay so it ends up making an almost painful sound as the relay chatters. The total current on the system is low enough with strip LEDs to be safe to use without a relay.

Don't understand what you mean by the dome light circuit not having enough "voltage" to activate the relay...

1. It's not voltage you're talking about its amperage. The truck system as a whole is all "12 Volt".

2. A relay is triggered by such a small amount of power (it's measured in milliamps) that you can trigger a relay from an OEM circuit and the trucks computer won't even recognize the parasitic drain, no error codes).

I will agree with you that in most cases, adding an LED or two, or even a low wattage strip light, won't hurt anything. That said, adding higher wattage accessories to certain OEM circuits need to be done carefully or you will end up with an unhappy computer, or worse, blown fuses or burnt wires.


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[Backwoodsram]

Don't understand what you mean by the dome light circuit not having enough "voltage" to activate the relay...

1. It's not voltage you're talking about its amperage. The truck system as a whole is all "12 Volt".

2. A relay is triggered by such a small amount of power (it's measured in milliamps) that you can trigger a relay from an OEM circuit and the trucks computer won't even recognize the parasitic drain, no error codes).

I will agree with you that in most cases, adding an LED or two, or even a low wattage strip light, won't hurt anything. That said, adding higher wattage accessories to certain OEM circuits need to be done carefully or you will end up with an unhappy computer, or worse, blown fuses or burnt wires.


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Yes the truck is a 12 volt dc system. However, the voltage to the dome light is stepped down under certain circumstance such as using the remote to unlock the door. Once you open a door the vehicle then supplies full voltage to the light which makes it go from dim to bright. The automotive relays you buy from most any retailer require 12-24 volts DC. Less than that and the relays like to chatter if the click over at all. I am an electrician by trade and have studied a wee bit of electrical engineering over the years, I am pretty sure I know the difference between voltage and amperage. You can calculate the amperage a circuit will pull by dividing the voltage of a circuit by the resistance on the circuit. The trucks computer does not adjust the amperage it sends to the lights to adjust the level of brightness. For example we will use the dimmer switch on the headlight panel. To dim the instrument lights you turn the rheostat (aka dimmer switch) to reduce or increase brightness. Adjusting the rheostat increases or reduces the resistance on the circuit. That resistance changes the amount of amperage the circuit will pull since the voltage on that particular circuit is fixed therefore increasing or decreasing the brightness of the lights. In the dome light circuit there is no rheostat to adjust resistance. The power is supplied to the light from the trucks computer, so the resistance on the circuit is fixed. To get the light to dim the computer sends a lower voltage than the normal 12 VDC to drop the amperage on the light and therefore dimming the light.

 

[jglass]

http://www.ramforum.com/f41/bed_lig..._mount_reverse_light_install_pic_heavy-66687/

This is one of the best threads I've seen on this topic. It seemed well done. I actually used it to install mine.
I put LED's in the bed and under the truck, and tied them into the cargo light trigger. It was very easy, took about half a day to do.
I did find that the factory circuits can't push the added lights. I used a low voltage relay from Elk, and a wire off the battery to fix that.

 

[Underarock13]

I have the big rig gen II ice bar LEDs. Installs not bad if you have the right tools and have an idea of where to find the wires.

 

[stevens]

okay, well mostly what ive seen here is tapping into the dome is the most common spot...will the dome wire run down to my driver side area? i gotta find the correct wire some how. ...so just find it splice and thats it...wallahh!?

 

[jglass]

I'm not sure about the dome, but the cargo light is white/tan and it is under the drivers door.

 

[stevens]

I'm not sure about the dome, but the cargo light is white/tan and it is under the drivers door.

under the drivers door? i wonder if all are the same color. sorry im kinda lost where about would this wire be exactly? :$

 

[TRXHemi]

Yes white and tan is the positive wire for the cargo light. I am tapping into that for mine..... I have two 6" x 2" LEDs that I am mounting under my rig.

 

[sbarron]

under the drivers door? i wonder if all are the same color. sorry im kinda lost where about would this wire be exactly? :$

Pull up the sill on the drivers side, either front or rear door. There will be a loom under the carpet. In that loom will be the white/tan wire.

 

[sbarron]

Yes the truck is a 12 volt dc system. However, the voltage to the dome light is stepped down under certain circumstance such as using the remote to unlock the door. Once you open a door the vehicle then supplies full voltage to the light which makes it go from dim to bright. The automotive relays you buy from most any retailer require 12-24 volts DC. Less than that and the relays like to chatter if the click over at all. I am an electrician by trade and have studied a wee bit of electrical engineering over the years, I am pretty sure I know the difference between voltage and amperage. You can calculate the amperage a circuit will pull by dividing the voltage of a circuit by the resistance on the circuit. The trucks computer does not adjust the amperage it sends to the lights to adjust the level of brightness. For example we will use the dimmer switch on the headlight panel. To dim the instrument lights you turn the rheostat (aka dimmer switch) to reduce or increase brightness. Adjusting the rheostat increases or reduces the resistance on the circuit. That resistance changes the amount of amperage the circuit will pull since the voltage on that particular circuit is fixed therefore increasing or decreasing the brightness of the lights. In the dome light circuit there is no rheostat to adjust resistance. The power is supplied to the light from the trucks computer, so the resistance on the circuit is fixed. To get the light to dim the computer sends a lower voltage than the normal 12 VDC to drop the amperage on the light and therefore dimming the light.

Oh, I see. Great explanation. Because you were tied running the relay from the "soft" voltage supplied by the dome light, the relay chatters open and closed as the voltage transitions, (while the lights brighten or dim)..

I tapped my system into the cargo light so avoided this.

Wasn't being a ****, just hadn't thought that issue through. Thanks for the clarification.

 

[jglass]

I went out and took some pictures. Hope this helps.

Right in front of the loom on the side is a big grounding lug you can run to. Also, this is the relay I used.

 

[Rzrman328]

Cargo light for my "custom" footwell lights I had to tap inside the left panel by the steering wheel.

Not fun.

 

[stevens]

I went out and took some pictures. Hope this helps.

Right in front of the loom on the side is a big grounding lug you can run to. Also, this is the relay I used.

okay and all of thoes are hidden on the drive side foot well sill correct? and the white and tan wire u got holding up is just what i need to splice into.?

 

[Backwoodsram]

Oh, I see. Great explanation. Because you were tied running the relay from the "soft" voltage supplied by the dome light, the relay chatters open and closed as the voltage transitions, (while the lights brighten or dim)..

I tapped my system into the cargo light so avoided this.

Wasn't being a ****, just hadn't thought that issue through. Thanks for the clarification.

No worries man. I wasn't very detailed in my first post. I tried tapping off of the cargo light, but that circuit cuts off too soon for my tastes, as well as I wanted the lights to come on when I opened the door.

 

[stevens]

No worries man. I wasn't very detailed in my first post. I tried tapping off of the cargo light, but that circuit cuts off too soon for my tastes, as well as I wanted the lights to come on when I opened the door.

where did u tap into? i also would like mine to stay on for a bit when i do a unlock etc. I'm just trying to find the easiest route here haha.

 

[sbarron]

Tapping into the cargo light (White/brown) will give you a delay during unlock. oyour lights won't however, come on with the door opening. You can turn them on manually with the cargo light switch

Tapping into the dome light makes them come on during unlock as well as having them come on when you open the door. You can turn them on with the dome light switch. That said, if you use a relay, you will run into the the relay chattering issue as stated by Backwoodsram (thanks again for the explanation).

easiest - either circuit without a relay.

 

[stevens]

Tapping into the cargo light (White/brown) will give you a delay during unlock. oyour lights won't however, come on with the door opening. You can turn them on manually with the cargo light switch

Tapping into the dome light makes them come on during unlock as well as having them come on when you open the door. You can turn them on with the dome light switch. That said, if you use a relay, you will run into the the relay chattering issue as stated by Backwoodsram (thanks again for the explanation).

easiest - either circuit without a relay.

if i tap into the dome, where would my wire be? color etc. And you say i dont need a relay right? just splice into the wire and im good to go. Just gotta find it

 

[sbarron]

Odds are you won't need a relay unless you're going off the reservation with some kind of high powered lights. That said, I don't know what lights, (wattage, quantity, etc) you are using so cant say for certain. That said, I used one.

Apologies, but I also can't swear to what color wire the dome light circuit is. I can say that the cargo is white/tan...

 

[stevens]

Odds are you won't need a relay unless you're going off the reservation with some kind of high powered lights. That said, I don't know what lights, (wattage, quantity, etc) you are using so cant say for certain. That said, I used one.

Apologies, but I also can't swear to what color wire the dome light circuit is. I can say that the cargo is white/tan...

i hear ya, thanks for all of this! any recommendations on the leds? i want them pretty bright ! i'd need 2x.

 

[sbarron]

I used 4 of these:

A-Series - Low Power - Single (Warm White) Surface... | Rigid Industries

I also have the lighting that came with my AMP Power Steps. The Rigids come on with he unlock. The lights for the AMP steps come in with the dome and/or opening a door.

Video... Warning.. the lights, truck and steps are FILTHY...
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