Roadblock in installing LED light-bar for Truck

Thread Starter

Samuel_adelman

Joined Jan 21, 2017
28
Greetings all,

I have recently fabricated my own "backrack" for my pickup truck and it looks spectacular. To put the finishing touch, I decided to install 2 LED lights on either side of the bar seen here: https://www.amazon.com/gp/product/B00IZ9VAOI/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Details:
LED Power: 36W (12 x 3W High Intensity LED)
Beam Pattern: Flood Beam
Input Voltage: 9-30V DC (fits 12V, 24V vehicles)
Working Lifespan: Over 30,000 hours
Working Temperature: -40~85 degrees Celsius
LED Color Temperature: Pure White 6000K-6500K
Material: 6063 Aluminum Profile, High quality Led Chips, PC Lens
Waterproof Rate: IP67; Waterproof, dustproof, quakeproof and anti-corrosive.

Voltage: 32V

So here is where things go wrong: I install the lights, combine the positives and negatives of both lights, and run the combined negatives of the 2 lights to the car battery. The positive combo runs to a throw switch at the dash, and back to the positive terminal of the battery. But, when I hook it up to the battery, it smokes and the wire becomes very hot.
I have triple checked all of the connections, there is
NO way I have the wires backwards, and all of the wires are in pristine condition. I have even removed the switch to see if the switch was causing issues, and I still get smoke at the battery.

Secondly, I can take these same wires and hook them up to an external battery in my Mahindra tractor, and the lights work perfectly fine.

So why on gods green earth can I take the same wires, attach them to the battery in my car and get smoke. but have working lights if I attach them to the tractor battery?

The car battery and the tractor battery are 12V batteries obviously, these lights are made for use with a car battery, the only difference in the cranking amperage of the batteries.

I am very very stuck, and would really appreciate some input.
 

crutschow

Joined Mar 14, 2008
25,242
You obviously have a short.
If it works with an external battery than it would seem some hot lead is accidentally connected to chassis ground.
Check for continuity between the hot lead and chassis.
The type of battery has nothing to do with it.
 

MrChips

Joined Oct 2, 2009
21,617
You stated that it smokes at the battery?
Where exactly does it smoke? Does the battery smoke or is it at the connection or at the cable leading to the connection?

I would have to hazard a guess that it would smoke at the weakest point where the resistance is the greatest.
 

Thread Starter

Samuel_adelman

Joined Jan 21, 2017
28
You obviously have a short.
If it works with an external battery than it would seem some hot lead is accidentally connected to chassis ground.
Check for continuity between the hot lead and chassis.
The type of battery has nothing to do with it.
That is what I thought, so I tested for it. I got a new pair of wires to run as a "test" to bypass the possibility of my routed wires shorting against a frame. The wires actually run to the tail-lights because my initial desire was to simply tap them into the reverse lights, but it blew the fuse ( now it seems that the problem was something else). From the tail lights, I then marry both the positives together and the negatives together underneath the bed, and then go to the battery/switch respectively. Simple. cut and dry.

Where I marry both lights underneath the bed/tailgate, I can attach both to the tractor battery: Lights work.

I then got a new pair of wires, ran it from the tail-lights location where I previously just successfully tested them (Because I know the problem isn't up to there) to the battery in the truck, where I get smoke and hot wire. I can then take that same new pair of wires, attach them to the tractor and have lights.

So as you can see, I got the same results from 2 sets of positive and negative wires. The use of the second pair to bypass the first pair that was routed underneath the truck eliminates the possibility of interference. The "test-wire" can be attached to the positive and negative terminals on a farm tractor and illuminate the lights, but smoke and get hot when attached to the car battery.
 

Thread Starter

Samuel_adelman

Joined Jan 21, 2017
28
You stated that it smokes at the battery?
Where exactly does it smoke? Does the battery smoke or is it at the connection or at the cable leading to the connection?

I would have to hazard a guess that it would smoke at the weakest point where the resistance is the greatest.
It is smoking because the plastic sheeting of the wire is burning. It starts first at the very tip of the exposed wire that makes contact with the positive terminal, and fairly quickly travels up the wire so much so you have to be careful when holding it.
 

crutschow

Joined Mar 14, 2008
25,242
So by testing for continuity, put one lead on the combined positives and the other lead on the combined negatives (not attached to battery) to see if the flow is unrestricted?
No.
You check the resistance between the combined hot leads and the vehicle chassis, to see if there's continuity (there shouldn't be).
 

Thread Starter

Samuel_adelman

Joined Jan 21, 2017
28
No.
You check the resistance between the combined hot leads and the vehicle chassis, to see if there's continuity (there shouldn't be).
Oh I see, to see if there is current running between them. Gotcha, will try tomorrow. Still doesn't explain why it would be fine when connected to the tractor battery but not with the truck battery.
 

crutschow

Joined Mar 14, 2008
25,242
Oh I see, to see if there is current running between them. Gotcha, will try tomorrow. Still doesn't explain why it would be fine when connected to the tractor battery but not with the truck battery.
It does if the tractor battery ground is not connected to the truck battery ground (which is connected to chassis).
 

Thread Starter

Samuel_adelman

Joined Jan 21, 2017
28
It does if the tractor battery ground is not connected to the truck battery ground (which is connected to chassis).
Okay I think I'm beginning to understand here, so this must mean that I am grounding out somewhere on the frame of the truck wherever it may be - really any surface of metal, correct? Because of this, every time I try to connect power to the battery in the truck its causing the positive lead to go all crazy. Now, with the tractor, because I'm still applying power to the leads but the tractor battery is grounded to another frame, I can get the lights to work.

In other words, when I connect the leads to the tractor battery, I still get light because the mistaken grounding of either of the leads is contained to the truck.

Do I have this correct so far?
So, I take my multimeter and set it to continuity or ohms I believe, have the positive lead touching the combined positives and the negative lead touching various surfaces of metal to see if there is any continuity. Will this be achievable even with a small battery operated multimeter? Will it have enough juice to travel through a significant amount of metal?
 

crutschow

Joined Mar 14, 2008
25,242
Do I have this correct so far?
Yes.
So, I take my multimeter and set it to continuity or ohms I believe, have the positive lead touching the combined positives and the negative lead touching various surfaces of metal to see if there is any continuity. Will this be achievable even with a small battery operated multimeter? Will it have enough juice to travel through a significant amount of metal?
Yes, the metal has very low resistance, so any continuity between the positive leads and the chassis can be readily detected by the meter.
 

Thread Starter

Samuel_adelman

Joined Jan 21, 2017
28
Yes.
Yes, the metal has very low resistance, so any continuity between the positive leads and the chassis can be readily detected by the meter.
I assume that it won't detect anything through paint or surface rust, correct?

I also got an idea, couldn't I unhook the truck battery and test the leads on it then? Without the battery being grounded? That would indicate there is indeed a short, right?
 
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