Just want to let you know that.. dome light has constant ON wired.. there there is two wire that makes the ground... ON and DOOR

 

I thought the dome light had a constant ground and was switched on by 12V.
In this case then you need to connect the black wire off of the relay socket to the negative dome light wire or negative door switch wire.

I would say switch the yellow wire with the red one. It would work the way you want but the relay would be energized all the time and would drain the battery over time.

Sorry for the confusion.

 

This isn't exactly ON TOPIC but have a similar problem. I would rather use a fuseable link (in the fuse box under drivers dash) vs. straight off the battery. Which is best to tap into? I have a fuse tap but have tried to use the cig lighter location but my cathodes wont light up. [setup: fusetap with 5a fuse - grounded from transformer to drivers kick panel bolt - power from fuse to switch (two pronged from Oznium) then switch to transformer] Please help, wouldl rather not run off battery. Thanks...not trying to threadjack, just adding on

 

Where is the negative dome/door wire?

 

Just rip out the dome housing and you'll see few wires there..
Use multimeter and find out which wire it is...

Get the color code and look under the dash that come down to the driver side pillar...

 

I believe it is the blue wire that connects to the dome light. and it goes down the drivers pillar. to behind the dash.
You can also tap into the door switch itself.
I am going to look at my car on lunch break to find the wire to tap into.
Sorry again about the confusion.

 

I have LEDs in my car that go on/off with the dome light and also have a switch so that I can turn them on whenever I want (i.e. inside the car driving). Sound familiar? Lol.

The information below is taken from a previous thread regarding a different placement of LEDs but with the same wiring setup (https://www.scionlife.com/forums/vie...374&highlight=<-- read both pages!):

This is where the negative dome light wire (blue) is and where you can get a constant 12V source (red):


This is the diagram I made quickly showing what I did for mine:


With the above setup (using an On-Off-On switch) you toggle between two different circuits. One "On" for the dome lights that will always go on with the dome lights and will dim off with them as well. The other "On" is the constant 12V to turn them on whenever you want. And the "Off" is self explanatory. A pointer though, the "On" you flick the switch towards will turn on the circuit on for the opposite prong. It makes no difference when doing the wiring, just when mounting the switch itself (i.e. if you want to flick it left for dome and right for constant 12v, etc).

Hopefully that makes sense. Let me know if you have more questions. Like I said, I have this in my car. Plus, I've installed it in customers cars and have helped others do the same setup. Good luck!

 

so t here was no relay needed in order to accomplish this?

 

and with this diagram i dont need a relay and it works fine with one ON being for dome, and the other ON being constant? with just one switch and nothing else?

 

No relay. One switch. Very easy. As I mentioned, you are toggling between 2 circuits. The negative lead from the LED goes into the middle prong and completes one circuit by connecting to the dome negative or the other circuit by connecting to the chassis ground point. Simple switch; this way for dome or that way for constant 12v.

 

alright but in order for me to actually make it so that the leds automatically go on with the dome light without a swith for that, but do have a switch to turn them on at any time....do i need a relay for that?

 

For that I guess so. I'm not sure (inexperienced with relays).

I understand what you're trying to do, but I just think it would be easier to do it this way IMHO. Because the dome light circuit is incomplete when the doors close, you would need a constant 12v & chassis ground to illuminate them when the doors are closed. You're plan is to then hit a switch from "Off" to "On" to turn them on (i.e. when inside the car with doors close). The way I'm proposing is the same thing (assuming you leave the switch in the "On" position for the dome all the time....like I do :D) but then you flick the switch from one "On" to the other. When you want the LEDs to turn off you flick it back over the dome "On" and you'll be all set for them to illuminate when you open the doors. As I mentioned, the dome circuit will be incomplete therefore not "work" so you'll be good. Probably about 1/4" of actual movement in the switch but does the same thing. Not much more travel but a lot less effort I think. I never have it in the "Off" position, just dome or 12v.