XC70: Electrical Best place to tap 12v for a USB adapter

[Bejam]

Hi All.

2011 XC70 D3 here. I've put a Tom Tom centrally in the windscreen and it's USB cable tracks neatly around under the windscreen to just behind the plastic dash end cap where the dash meets the door (it can go either to driver or passenger side).

Can anyone please recommend an easy wire to tap 12v for a USB power supply?

Ideally, one that cuts out after a period of time, once the ignition is switched off.

Cheers,

Ben.

[andyg]

Your best bet probably is from the internal fuze box that normally is mounted hidden under the dashboard at about knee height. On my S80 there is one on the passenger side and hopefully your XC70 is similar. Look at your handbook and you should be able to identify a fuze for an item that is switched live/off with the ignition. You can tap 12v from that using one of these:

https://www.ebay.co.uk/itm/12V-24V-A...cAAOSwIYpckVWo

That gets you a 12v positive lead. Of course you will also need to run a ground (earth) lead that you can also get from the fuze box and connect them with your TomTom lead.

If you are not happy playing about with fuze boxes and connecting leads etc, then test your rear passenger 12v socket. That is the old cigarette lighter type. On my S80 that is switched live/off with the ignition. If yours is the same, then by using a USB adapter from that socket you could take a long USB socket extension cable (say 3m) forward, tucked under the centre tunnel armrest and then across under the carpet to meet up with your TomTom cable at the dash end cap. See:

https://www.ebay.co.uk/itm/Dual-USB-..._1lhXfIya9iBHw

https://www.ebay.co.uk/itm/5m-LONG-U...cz4iS9Ez87vIjA

You may also have a 12v and a USB socket in the cubby under the centre armrest that you could use with a shorter extension lead? But I think they are permanently live. It is not great to have auxiliary equipment permanently connected and drawing even a residual current. Over time that can lead to low battery warnings and other strange things!

[Bejam]

Thanks Andy. I wasn't aware of piggy back fuse taps like that - very useful to know. In the meantime, after some head scratching, I tapped off the glovebox light, which proved to be a timed on/off as well - it goes off after 2 mins of locking the car, but also wakes up the sat nav as soon as I unlock it.

It seems to be OK for now, but I think that fuse tap may prove to be a better long term solution.

Ben.

Originally Posted by andyg

Your best bet probably is from the internal fuze box that normally is mounted hidden under the dashboard at about knee height. On my S80 there is one on the passenger side and hopefully your XC70 is similar. Look at your handbook and you should be able to identify a fuze for an item that is switched live/off with the ignition. You can tap 12v from that using one of these:

https://www.ebay.co.uk/itm/12V-24V-A...cAAOSwIYpckVWo

That gets you a 12v positive lead. Of course you will also need to run a ground (earth) lead that you can also get from the fuze box and connect them with your TomTom lead.

If you are not happy playing about with fuze boxes and connecting leads etc, then test your rear passenger 12v socket. That is the old cigarette lighter type. On my S80 that is switched live/off with the ignition. If yours is the same, then by using a USB adapter from that socket you could take a long USB socket extension cable (say 3m) forward, tucked under the centre tunnel armrest and then across under the carpet to meet up with your TomTom cable at the dash end cap. See:

https://www.ebay.co.uk/itm/Dual-USB-..._1lhXfIya9iBHw

https://www.ebay.co.uk/itm/5m-LONG-U...cz4iS9Ez87vIjA

You may also have a 12v and a USB socket in the cubby under the centre armrest that you could use with a shorter extension lead? But I think they are permanently live. It is not great to have auxiliary equipment permanently connected and drawing even a residual current. Over time that can lead to low battery warnings and other strange things!

[Tatsfield]

wakes up the sat nav as soon as I unlock it

It? Just for clarity, unlock the glove box or the car or the ignition?

You need to select a fuse that provides current when the ignition is turned on. The TomTom can be set to switch on when it receives the charging current.

Might I also suggest that you mount the device in the lower right corner of the windscreen where its touch screen falls to hand more easily, doesn't obstruct any meaningful forward view and is closest to your line of sight while not taking your eyes off the road. That is the more ergonomic placing. Central mounting is to do with unnecessary symmetry but not ergonomics.

[Clan]

Originally Posted by Bejam

Hi All.

2011 XC70 D3 here. I've put a Tom Tom centrally in the windscreen and it's USB cable tracks neatly around under the windscreen to just behind the plastic dash end cap where the dash meets the door (it can go either to driver or passenger side).

Can anyone please recommend an easy wire to tap 12v for a USB power supply?

Ideally, one that cuts out after a period of time, once the ignition is switched off.

Cheers,

Ben.

The professional place to take this feed from is the wires under the 12v Power socket , that is where volvo tap in for their accessories .

[Bejam]

Originally Posted by Tatsfield

It? Just for clarity, unlock the glove box or the car or the ignition?

When I unlock the car. The glovebox light circuit is configured to wake up when the car is unlocked. It goes to sleep a couple of minutes or so after locking the car.

[Bejam]

Originally Posted by Clan

The professional place to take this feed from is the wires under the 12v Power socket , that is where volvo tap in for their accessories .

I was struggling to work out how to extract the rubber grommets that cover the screws between the binnacle and the gear-lever cover trim, so that's why I went for the glovebox light as a temporary measure.

I've ordered a fusebox tap, further to the advice further up. I think this might be an elegant solution. The Tom Tom USB supply isn't drawing a huge current and I've put a dedicated USB supply, made from butchering and soldering a regular 12v USB adapter, behind the dash end cap, so it's only going to be used for the TomTom.

[Bejam]

Originally Posted by Tatsfield

Might I also suggest that you mount the device in the lower right corner of the windscreen where its touch screen falls to hand more easily, doesn't obstruct any meaningful forward view and is closest to your line of sight while not taking your eyes off the road. That is the more ergonomic placing. Central mounting is to do with unnecessary symmetry but not ergonomics.

Er, no. I'm quite happy with where I've placed it - and prefer to let my passenger fiddle with it, rather than me. Thanks for the suggestion, though. :-)

[andyg]

Originally Posted by Clan

The professional place to take this feed from is the wires under the 12v Power socket , that is where volvo tap in for their accessories .

As ever Clan's advice is spot on! Indeed I have an aftermarket DAB radio in the boot of my S80 where the power is tapped from the back of the passenger compartment 12v socket. All cables hidden away and it works very well, with no residual current drain etc. The original OP was looking to mount his satnav on the windscreen so that is why I suggested the front fuze compartment just to reduce long cable runs. However, there is more scope for problems playing around with fuze boxes compared to taking a simple tap from an existing socket.

[mhon72]

Originally Posted by Bejam

I was struggling to work out how to extract the rubber grommets that cover the screws between the binnacle and the gear-lever cover trim, so that's why I went for the glovebox light as a temporary measure.

I've ordered a fusebox tap, further to the advice further up. I think this might be an elegant solution. The Tom Tom USB supply isn't drawing a huge current and I've put a dedicated USB supply, made from butchering and soldering a regular 12v USB adapter, behind the dash end cap, so it's only going to be used for the TomTom.

The rubber grommets are attached to a plastic base which clips into the console to cover those mounting screw.