Finding the wire coming from a specific fuse (2018 Leaf)

[hbquikcomjamesl]

Does anybody here know of an easy way to locate the wire coming off of a specific fuse (in this case, most likely the driver-side seat heater fuse) in the interior fusebox?

So far, back when I put in my "Flap Ajar" indicator and the dedicated socket for my GPS navigator, I simply tied into the wire feeding the center console power socket, but that doesn't exactly cut it for this project.

Given that a factory seat heater switch would go into the center console, next to the USB port and the power socket, would the lines from the seat heater fuses already be run to that area?

 

[hbquikcomjamesl]

I now know two things I didn't know before:

1. The seat heater fuses are on the "battery" bus. This means I'll need to rig one more relay in the control circuit. No big deal, although it would be nice to be able to energize that relay only when the car is fully powered up. (I'll take accessory bus, given that it times out, and that I've already got a wire on the power socket.)
2. If there's a wire running from the seat heater fuse to where the factory seat heater switches are located, I can't find it.

 

[GerryAZ]

I now know two things I didn't know before:

1. The seat heater fuses are on the "battery" bus. This means I'll need to rig one more relay in the control circuit. No big deal, although it would be nice to be able to energize that relay only when the car is fully powered up. (I'll take accessory bus, given that it times out, and that I've already got a wire on the power socket.)
2. If there's a wire running from the seat heater fuse to where the factory seat heater switches are located, I can't find it.

I don't know what year/model LEAF you have, but I think the power to the seat heaters for most models is controlled by the A/C control system so that the switches only get power if the climate control timer or remote climate control is active or the car is in READY mode.

 

[hbquikcomjamesl]

I don't know what year/model LEAF you have, but I think the power to the seat heaters for most models is controlled by the A/C control system so that the switches only get power if the climate control timer or remote climate control is active or the car is in READY mode.

Great, but where would I tap into that? There's definitely no separate place on the back of the HVAC panel to plug in seat heaters.

Lacking anything else, I've ordered an extra relay, so that I can slave the seat heater power to something else, and if nothing else presents itself, I'll just slave it to the line I've already installed to power my GPS navigator and my "Flap Ajar" indicator off the "lighter" socket.

 

[hbquikcomjamesl]

Yesterday, I learned, once and for all, how to get at the back side of the fusebox. Much more difficult than on old Arabella, my 1978 510.

On a 2018 left-hand drive, you need to pull off the fusebox cover, undo enough of the lower dashboard to get hands and tools inside, and also pull the port outboard vent grille assembly, to the left of the instrument cluster.

With the fusebox cover removed, you can see and remove two screws holding the fusebox brackets to the dashboard frame. Adjacent to those screws are sliding clips, integral to the brackets, that go into holes in the dashboard frame. Slide the fusebox up, and it comes right off. It will remain attached to a rather short, rather heavy cable, though, so you're going to have to work on it in place.

Figure out which fuse you want to tie into, and then use a voltmeter, with the negative lead clipped to grounded metal, and a long positive probe inserted in the wiring holes on the back side of the fusebox, to verify that you actually have the wire you think you do. You want to make multiple tests for this, ideally pulling and replacing the fuse with the probe in place and making contact, before you do anything that would be difficult to undo.

There is just barely enough room to snap an appropriately sized "suitcase connector" on the wire, insert another wire to tap in, and carefully drive the blade home with pliers (taking care to avoid severing the wire). But if you're careful, there should be plenty of room to keep the pliers well clear of grounded metal while you're doing it.