[ChibbMD]

I had a hard time finding this information when I was looking for switched power in the trunk fuse box. I saw another post asking about it today, so I thought I would put the information here for future reference.

In the trunk fuse box there is a purple wire that allows you to tap into the accesory circuit. This is only powered when the ignition is in the ACC or ON position.

In the pic below, refer to the purple wire with the red arrow pointing at it. Not the one with the probe. Hope this is helpful.

[radz28]

KUDOS AND THANKS!!!

[h018871]

I was adding some Wide bands and wanted switched power. This is the ticket!
I was wondering if there are any switched fuses so I could use an "add a circuit" instead of a tap. Lots of angst and investigation later, there are some!

F33-WCM "wireless charger"
F19-frt vent seat
F17-Spare
F12-htd str whl

I used the spare, F17, circled in yellow.
the other add a circuit is for an intercom, it is in F23, BCM 1, constant 12v

Thx to ChibbMD for getting this started!

[bandier]

Is there a post anywhere as to working of this to Add-A-Curcuit. I need to add an accessory that's 12v and 15-20a. With a little guidance as to 'how to' work off of the noted extra or unsed trunk switched power fuses, I can take if from there. Just need a bit more detail...

[bishopts]

Some of those empty fuse slots have one terminal in them. They are battery hot or key hot, they can be used to add devices without requiring a piggyback jumper. If you can't get your probe down in the cavity to test for key hot, use a spare fuse as an extension.

[h018871]

Try googling “how to 12v add a fuse tap”

It’s pretty straightforward, keep in mind that the supply wire into the fuse block is now carrying additional load due to the additional circuit.

[bishopts]

Originally Posted by h018871

Try googling “how to 12v add a fuse tap”

It’s pretty straightforward, keep in mind that the supply wire into the fuse block is now carrying additional load due to the additional circuit.

That's why i suggested using an empty slot vs a piggyback.

Also piggyback connectors can keep some circuits on because modules that control the circuit you're piggybacked into will backfeed into the addition and think it's own circuit is still active.

Empty slots are usually fed by high amp fuses to the fuse slot, when you look down in them you will see a single terminal in the empty fuse slot. Since the second slot isn't there then there is no chance of keeping a module awake from it. The piggyback connector your using will then only feed the addition you added.

[2018 Blue 1LE]

Originally Posted by bishopts

Some of those empty fuse slots have one terminal in them. They are battery hot or key hot, they can be used to add devices without requiring a piggyback jumper. If you can't get your probe down in the cavity to test for key hot, use a spare fuse as an extension.

How are you utilizing a slot with only one tab in it?


Is it hot(switched or always) and by simply dropping in an add a tap(or similar) you get the power to the fuse ?


I have tried to figure a way to add the other tap and then a fuse to make it look factory.

[bishopts]

Originally Posted by 2018 Blue 1LE

How are you utilizing a slot with only one tab in it?


Is it hot(switched or always) and by simply dropping in an add a tap(or similar) you get the power to the fuse ?


I have tried to figure a way to add the other tap and then a fuse to make it look factory.

Inside the fusebox is setup like a power bus. The fuses are grouped to share a common feed to the fuse and then away from the fuse is their each own dedicated path to the source they feed.

Think of it like this.
4 fuses for emissions control will have one power feed to the left side of each fuse. But the right legs will all go to each individual device.
So purge solenoid has a wire coming from one fuse to the solenoid and then the circuit completes in the pcm so that the pcm can activate it by applying ground.
Vent solenoid is setup the same way using another of those 4 fuses.
The next 2 are o2 heaters that again come from the right legs of the fuse to the sensor heaters and complete in the pcm.
So using that as a reference idea. Lets say in the fusebox buss there was a 5th unused fuse hole. It has the same power in but no way to go out. If you use a piggyback fuse adapter then it will plug down into the power supply in that empty slot and from the adapter you can send the power to whatever device you're trying to get working.

Each fusebox will be slightly different from vehicle to vehicle. So you will just need to test if the single pin is key hot or battery hot.