I've read just about every post in here related to interior lighting and dome lights. From what I've learned, it is very possible to fry some wires by overloading the dome light's circuit. I am very interested in having interior lights that are in sync with the dome light but I don't want to end up telling another horror story about fried components due to messing with the dome light circuit.

I plan on installing the grab handle (or 'oh $hit bar') led lights but I want them to function just like the dome light - on when the doors are open and when the keyless entry is activated, off when the doors are closed. The fading is not essential but it is preferred.
What I've learned is that while cold cathodes use a converter to go from 12v to some much higher number that escapes my memory, leds draw much less power.

So, my question is, can I hook up all four grab handle leds to the dome light terminals without fear of damaging any components? Mind you I will not be installing the footwell cathodes in sync with the dome light...unless this were possible without using a relay and without causing a fire.

I am a complete noob to car mods and any help i can get is greatly appreciated.

 

I was unfortunately one of those horror stories. I had LED's everywhere as well as my 2 sets of cathodes hooked up to the dome light. Everything worked fine in mine for months until some wires shorted. However, that was due to the fact that I was sloppier in my early days of hooking up the LED's (I did them in sections over a few months) and one wire shorted (so it shorted the door lock control relay attached to the dome light).

So, as long as you aren't sloppy in your hookup (heat shrink or electrical tape the hell out of it), nothing should actually overload the electrical circuit of the dome light.

 

I would be carefull with hooking up lots of lights to this circuit. I would not hesitate to hook up 4-6 small cathodes to it tho....or a few leds....both draw very little power. The problem comes when you wire many many lamps to one circuit. Make sure to wire your added light set up and then put a fuse (rated lower than the dome lamp circuit) just before you go to the power. That way if you do get a short in the added lamps the fuse will blow before taxing the dome lamp circuit itself.

 

thanks for the quick replies. i'll make sure to add fuses to the wiring before the dome light circuit. i've never done this before but i saw the write up here and it was done quite well.

does anyone know exactly what inline fuse i should use? i don't even know what the dome light fuse is rated as.

many thanks.

 

The interior lighting circuit is fused at 7.5A. At 12V the 8W dome light pulls about .7A of current. There is probably some room to play, I have 20W interior lighting with no blown fuses or melting wires.

Most of the fuses are mini-blade type fuses, so might as well use those. Wal-Mart has a "Mini Blade Type Inline Fuse Holder" that looks like this:



To be honest I don't think adding additional fuses beyond the dome light fuse will save you anything. If you had a 5A fuse between the dome light and your LED wires, and you shorted on your LED wires, the whole circuit is going to see the current in the milliseconds it takes for the 5A fuse to blow. It may even blow the 7.5A fuse on the dome light, or both. It will not add much protection and make for more splicing, which increases the chances of a short.

I did short the interior lighting circuit when I pulled the wrong fuse installing my front dome light, and after I replaced the 7.5A fuse it was good as new.

I think for the LEDs they may not be rated for 12V so if you add them you might cause them to short. What LEDs are you using?

 

I have 32 leds wired to my dome light and it seems to work fine. I made 8 sets of 4 leds wired in series and then wired the 8 sets in parallel to each other. This setup works for me, but it did take some trial and error. I originally had them in sets of three and burned some of them out because the voltage was too high.

Some will tell you that you need a resistor on every led. I am sure it is much safer for the leds that way, but I chose not to because the resistors just add more of a load to the already weak circuit.

Plan it right, and take your time wiring it and you shouldn't have any issues. You can build your circuit and test it separate from the dome light to make sure everything works, then hook it up to the dome.

I would recommend disconnecting the battery while connecting anything to the dome light. After everything is in, double check your work to make sure there is no possibility for a short then reconnect the battery.

 

You can also just pull the dome light fuse from the fuse box in the engine bay. You lose your radio presets either way.

 

understood. thanks again.

I'm getting some flexible led strips from oznium.com for the grab handles. It says that they don't need any resistors, probably because there are enough leds in the series.

If I were to get an inline fuse anyway, what should the amperage be?

 

7.5A

The 6ft strip they have only draws 1.2A:

http://www.oznium.com/led-flex-strips/tech

 

what strips are you using and where are you getting them? i want to do this.... but now im scared!