Hooking up a 12v DC LED strip box to Automotive wiring?

Okay so the only AC adapter i had is kind of unreliable, asuming i know what i'm doing here (putting the RED MM lead inside the plug and the black on the ouside, even tho its a 12v AC adapter my MM is saying its putting out 15.80 volts.. okay... kinda strong, but i tried it anyways, only on the NEW box becuase the new box has a plug hole just for an AC adapter. So here's my findings with the NEW box.

With the AC adapter hooked up, the NEW box, with the MM RED lead on the 12v pin and the Black MM lead on one of the other leads (Blue colored lights i believe) It was showing 15v's making it through the box to the end of the pins! Also with this box i was able to use the remote control, and off was working, when i was swapping colors the voltage would drop depending on what color (like red only was giving the BLUE ground pin a 0 volts read out, but BLUE selected was giving it a full 15 volts read out. So in my very rough experiment here, this AC adapter plug was making the unit work!

I righted up some wires taped to the AC adapter (i know i know not very GOOD thing to do but i did it anyways) and so far on the OLD BOX things look okay, but I cant get any readings on the connector that would go to the lights, so i'm gonna unsoldier them and res soldier them just in case, When i tested the solder points on the board that the connector goes to, they all measured correctly! 14v at the end! the 7805 was reading 14.8 something going in on the first pin and reading 5.02 on the 3rd pin when measuring using your list, So it does sound like its something in my car or the wiring i have set up. I'm not sure how i'll even trouble shoot that, but its wierd to know that the box itself might have been working fine the entire time. Will report back on the old back after i have the leads read soldered.

Okay i was wrong they didnt need re-soldering. After some more testing it appears to be working fine off the ac adapter as well.... so at this point i need to figure out how else i can get power to them the way i'd like. Is there any way to trouble shoot why the place i'm leeching the power now isn't sufficient now while it used to be for 6 months?

Do you have addishonal wires in the car hooked up to the cars wires or does the box hook up right to the car wires?
What are you using for the ground in the car?
Is anything eles not working in the car?
Are the dash lights bright?

The car has a wire that comes from one of the harnesses that goes up to the incandesent bulb in the glove box, I hooked a car splicer clamp thingy to this with an extra wire running down, which used to run directly into the box, then a few weeks later i got a 'kill switch' so i could turn the lights off quickly and easily in case a cop drove past or anything. I cliped the wire going to the box, and then soldiered it up to a longer wire that went over to the kill switch, then a wire from the killswitch back to this box (the older box). The negative lead is hooked up to the negative lead of the light bulb in the glove box's wire. so thast where i'm getting the ground from. This set up worked great for a matter of months, then one day, i saw the lights kind of dim a bit and flicker, but then return to normal brightness and continue to work for a week or so, then they went dim and went off and did not return.

Everything else in the car appears to be working ok, the stereo, the dash lights, the dome light, the door lights, the glove box light. The dash lights appear to be about as bright as they always were. If my car battery was going bad, would that be the cuase of all this? I mean would it still make the boxes not work even if the car was started and running?

If my car battery was going bad, would that be the cuase of all this? I mean would it still make the boxes not work even if the car was started and running?

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No thats not it.

I hooked a car splicer clamp thingy

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Those things are not good at all. Remove it and solder the tap wire to the car wire.

few weeks later i got a 'kill switch'

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How long did it work after you installed the kill switch? maybe its bad. Can you bypass it for testing?

The negative lead is hooked up to the negative lead of the light bulb in the glove box's wire.

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You should tie the negative lead of the controller box to the body of the car to inshore a good return path. Sometimes the dash light negatives go through the dimmer.

4pyros said:

No thats not it.

Those things are not good at all. Remove it and solder the tap wire to the car wire.

How long did it work after you installed the kill switch? maybe its bad. Can you bypass it for testing?

You should tie the negative lead of the controller box to the body of the car to inshore a good return path. Sometimes the dash light negatives go through the dimmer.

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Okay will try to trouble shoot those things... I apparently cannot start the car now.. I dont know if just coincidence or not, but it wont turn over it tries then winds down and goes click click click click very fast, so my battery may have died with all my testing... my luck! (all my lights in the car still work fine though..)

diy a led strip on car is that hard, it's cheaper to buy a new one instead of extending its life...

It may not be the strip thats bad though, might be my car!


The battery issue could be related to the snow we just got, apparently some battery's dont output enough to start a car in really cold tempatures.. This might be put on hold for a day untill the warmer rainy weather comes back. (seattle)

This might be put on hold for a day untill the warmer rainy weather comes back. (seattle)

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You should put that in your profile.

I figured it out!

Originally when i set this whole thing up, i ran a long wire to my kill switch on my passenger side, but at the time I did not have a way to get a soldering iron out to my car (i lived in a condo) so i used these little automtive peices (shown below) to splice the wire going to the switch and to also splice the wire coming from the switch.. I remember having a little issue with these at first, but they worked okay for a few months.. But these were the problem becuase i cut them off the wires and simply twisted the wires together and viola! the whole thing works great again. It's true I do still have the 'crimp down' type of auto motive connectors being used from the glove box light down to the unit still, but i am hoping those wont have the same issues these little peices of crap did.

For the time being I am leaving the wires all twisted together untill i can get to a friends house and use an extension cord from his guarage to properly soldier the stuff together. First things first though, i'm gonna need a new car battery i think. I still cant get it to turn over. (although everything else works great, the stereo, the alarm, the lights.

but anyways I wanted to say thank you to all the Electro community who helped me troubleshoot this and espically to 4pyros. Thank you sooo much for your time and suggestions that ultimately led to the solution to this problem! I shoulda came here right when it failed! Thanks again!!!


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electricview said:

I figured it out!

Originally when i set this whole thing up, i ran a long wire to my kill switch on my passenger side, but at the time I did not have a way to get a soldering iron out to my car (i lived in a condo) so i used these little automtive peices (shown below) to splice the wire going to the switch and to also splice the wire coming from the switch.. I remember having a little issue with these at first, but they worked okay for a few months.. But these were the problem becuase i cut them off the wires and simply twisted the wires together and viola! the whole thing works great again. It's true I do still have the 'crimp down' type of auto motive connectors being used from the glove box light down to the unit still, but i am hoping those wont have the same issues these little peices of crap did.

For the time being I am leaving the wires all twisted together untill i can get to a friends house and use an extension cord from his guarage to properly soldier the stuff together. First things first though, i'm gonna need a new car battery i think. I still cant get it to turn over. (although everything else works great, the stereo, the alarm, the lights.

but anyways I wanted to say thank you to all the Electro community who helped me troubleshoot this and espically to 4pyros. Thank you sooo much for your time and suggestions that ultimately led to the solution to this problem! I shoulda came here right when it failed! Thanks again!!!


**broken link removed**

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It doesn't look like you used the proper crimp tool on those bullet connectors.

Very possible.. I just got everything soldered together today so i feel much better about it now. Originally I used these crimp connectors becuase I wanted to be able to remove the kill switch eaisly without having to snip or resolder wires, but i guess these peices were not made to be removed and re plugged in.

but i guess these peices were not made to be removed and re plugged in.

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Thay are ment to be connected and disconnected but with out the proper crimp tool thay well fall off the wire.
You can solder these molded ones to your wires and thay well be good;
https://www.allelectronics.com/make-a-store/item/CON-319/2-CONDUCTOR-WEATHER-RESISTANT-CONNECTOR-14AWG/1.html

Okay so hopefully someone will be able to answer my question by resurrecting this thread.
I would like to know what the component is called that you are hooking up to your vehicle 12v wiring to hook up to your LED ribbon?

I just finished remodeling my wife’s kitchen and used 16 foot cool LED strip lighting for under counter lighting and used a 120v house current to 12v transformer. SO I got the great idea to try using the same type of thing for lighting in my RV remodel project. I tried hooking a LED strip directly to the car battery and…..nothing???

So I figure I need some sort of automotive 12v to 12v LED ribbon thingy. I know there has to be some sort of simple thingy that I can probably get through Amazon for some kind of reasonable price. I don’t want multi-color capability or remote control; just want plain white and a simple on/off switch. I don’t know squat about electricity. Just enough to be dangerous enough to try stuff myself. So a little simple explanation would be appreciated. Reading this thread left me scratching my head wondering WTH. However I started thinking really early that maybe something was wrong with the 12v auto source wire.

Thank You

You need to point or post a pic to what you have. The gist of the problem is that LED's are CURRENT DRIVEN, not voltage driven. So, the simplest way to drive an LED is to use a fixed voltage power supply, a resistor and a string of LED's.

Not using the resistor can kill a string.

The better way is to use a LED controller which will be a current source.

Now it is poosible that you have something like this: https://www.amazon.com/dp/B0053V1NH...e=asn&creative=395105&creativeASIN=B0053V1NHA

In which case it isn;t current controlled. LED polarity is important, but damage is somewhat possible if hooked up backwards.

If your in the US, you might want to invest in a $5.00 multimeter from Harbor Freight.

the link you sent is for a 120v house AC system to 12v
have that in the house
I'm looking for something to hook up to the van 12v system that will power the LED string

True. I need a pic of the controller of what you have. If it's a 12 VDC fixed voltage source, then you would not need anything else.

If it has to be current limited, then you need something else.

You can also get strips designed for the car: https://www.hero-ledstore.com/led-auto-car-light-car-auto-led-strip-c-23_100.html

This is an example of a Naked LED controller: https://www.electro-tech-online.com/custompdfs/2013/01/ald6.pdf It would require a LOT of work to make it work, but it gives you an idea.

Without specs of some sort, it's difficult to suggest anything except pitfalls to avoid. A few measurements would help.

e.g take the current controller and measure it's output in terms of voltage and current when connected to a string and how many LEDs and how many LEDs in series and parallel.

Each LED may drop about 2.1 volts and need about 50 mA of current, but these numbers can vary greatly.

I just finished remodeling my wife’s kitchen and used 16 foot cool LED strip lighting for under counter lighting and used a 120v house current to 12v transformer.

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Is your LED strip ment for 12 volts DC or AC?
Can you test your strip in the House?

I'm having a hard time finding stuff applicable. Here is just one item: https://www.electro-tech-online.com/custompdfs/2013/01/DS_TALEXX_C350-2_12-24V_en.pdf

This is for 350 mA and it might be too high of a current. So, that's why we need as much info as you can get. VA, number of LEDs in parallel or series etc.

Just poking around, noticed this and thought I'd add a suggestion.

Wiring LED's to house power is always a pia due to access problems for cords, etc. I found a twelve volt battery, used as back-up in emergency exit signs, will run my LED string for hours, and they are only used PRN anyway. Finding a corner for the 6"x3"x3" battery in the back corner of a cabinet was easy, as was drilling a single access hole. When the lights dim every month, I hook up a charger and I'm back in business. My batteries are old ($2) and new ones may last much longer. Running a 25 lamp strip.

Best wishes