Dome light control (ground)

Running LED bed lights and looking for a place to tie into the dome control. My search keeps leading me to the drivers side A-pillar.

http://www.tacomaworld.com/forum/lighting/106251-diy-running-board-lights-ground-lights.html

http://www.tacomaworld.com/forum/technical-chat/4838-cheap-free-mods-18.html#post297835

I am not a huge fan of spicing at that location. Does anyone know where the other end of that wire terminates? I don't like the A-pillar because it looks like I have some airbag stuff in there. I don't like to mess with things around the airbags.

I have tried to follow the wire bundle down behind the dash, near the fuse panel but it gets lost. It's got do be there somewhere.

Anyone know?

 

Wow! That's perfect!

Thanks.

 

Would I be correct in assuming that this would also be an acceptable location to apply a ground to activate the interior light via an aftermarket alarm system, or would it be better to tap in at the A-pillar and diode-isolate so there is no feedback going to the OE system?

Similar question on the parking light "flash" from an alarm... can it safely backfeed into the "tail" fuseholder slot?

Also, to enable the "lock on ignition/unlock on off" I need a tap that is hot in both run and start... would the power outlet tap be good for this?

 

Caribe Makaira

Where did you find that junction box wiring diagram? I am trying to get into power after the dome fuse but before it goes to the body ECU (blue wire you described). Basically trying to duplicate the map light circuit for a low-draw bed light.

Thanks

 

You can't use the dome circuit to drive a relay to power bed lights.
Because of the dimming when shutting off, the relay will chatter.

The blue wire can be found most easily under the driver's A-pillar cover.
Follow it down from there to the kickpanel junction.

Remember... the dome circuit is ground-true. Power goes through the fuse, and to the dome light.
At the dome light, you can switch it between open (light off), blue wire (on with door), and ground (on 24/7).
When you open the door, it sends a signal to the BCU, which applies a ground to the blue wire.

If you tap into the blue wire, run it to the bed lights, and ground the other side of the bed lights, both the dome and bed lights will be wired in series and will be on (very dimly) until the battery runs down OR until you switch the dome from "door" to either "off" or "on"

With the dome set to "off" or "on", the blue wire receives no power.

 

I ran wires for this and installed a Carling V switch this afternoon and plan on finishing tomorrow when the lights arrive tomorrow.

I studied the wiring diagram and found that the map lights are wired to the same circuit as, but are not affected by, the dome light; it just shares a fuse. So I am not really going to use the dome circuit to drive this, just tapping into the 'always on' lead that comes from the engine room fuse block before it becomes the dome circuit in the driver side junction box. Basically duplicating the map light wiring.

This is how I am planning to wire in the lights so that they are on the 7.5A dome fuse but are independent of that switch. It will be ground-true, just like the dome and map lights.
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I located the 12v leads for the dome and map circuits (The two white wires) with my volt meter, and will figure out which is which tomorrow. I wanted to tap into it prior to this point but that seems like a lot of work. You can see the evidence of my optimism on the above photo.

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From here I have a red wire running to the bed lights and a black wire running back up to the rocker switch, making it ground-true.

Am I missing something or does this look like it will work?

 

My concern is adding the bed lights would overload the ground circuit in the B/ECU.
You've already got the dome, and map lights. Another 7.5a circuit could be too much.

Granted, LED bed lights are low draw, but I would make sure to replace the dome and map lights with LED as well to hold the total load on the ground (blue wire) to no more than stock levels.

 

His bed lights are likely less than 2 amps. This isn't an issue.
id have just tapped them into the dome light. No fuss, no switches no wiring schematics. Just bed lights that work when they are supposed to.

 

The Led lights are ~2amps. And if I understand things correctly, the way I have wired this the ECU is isolated from this circuit.

 

I have to agree with Racer on this one Rich. Since he is drawing power off in parallel BEFORE the power reaches the dome or map circuits, then the only additional load will be on the fuse itself. Of course if that fuse is only 7.5A, and you are controlling a relay with it, then it is not the amperage of the bed lights that is the concern, it is the amperage of the RELAY. So I would check to see how many amps your relay is going to draw (Both switch-on power and steady-state) and check to see if the wire from the fuse is of the right gauge, and that the fuse itself is large enough. (Unless I misunderstand the drawing added to the wiring diagram and the bed lights themselves will be directly powered from this fuse, then you need to just add in the amperage of the bed lights as well as the factory lights to be sure the wiring and fuse are correct.

 

Thanks for the feedback Bama. I am not using a relay, but my drawing does make it look that way. Either way I did not think about the amperage draw from a relay being a factor! That piece of info will come in handy, I would imagine.

 

Yeah, with relays you have to worry about two different draws. The switch-on, which is the power it draws when the relay is first energized. This current can sometimes be TWICE that of the steady-state draw, which is the draw while the relay remains on. Relays do also tend to "spike" when turned off, so when using a relay piggy-backed to an existing circuit, you might want to consider putting a diode in parallel with the relay, similar to what they use for A/C compressor clutch coils. This all depends of course on where you are tapping in your power at. As a rule of thumb I always say better to do more than not enough.

 

Okay cool. I got the impression that the intent was for the bed lights to be triggered with the dome.

 

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