Fuse Box - Permanent Live

Faults and Technical chat for the Volvo XC40
eugen61
Posts: 1261
Joined: Sun May 10, 2020 7:33 am

Post by eugen61 »

From the owner’s manual: “Incorrect connection and installation of software or diagnostic tools may have a negative effect on the car's electronic system.
We strongly recommend that Volvo owners only install Volvo approved original accessories, and that installation of accessories is only carried out by trained and qualified Volvo service technicians. Certain accessories only function when associated software is installed in the car's computer system. Volvo Cars accepts no liability for the consequences if unauthorized equipment is connected to the On-board Diagnostic socket (OBDII). This socket should only be used by trained and qualified Volvo service technicians.”

K9plus1
Posts: 27
Joined: Mon Nov 20, 2023 9:37 am

Post by K9plus1 »

After some research, Those odb power cables only provide VCC+ on one of the pins. There isn't a switched, live pin to signal the car is turned on/off. So they don't work with dash cams needing a temp/switched supply.

Huge shout out to the guys who found the 2 fuses no. 12 (permanent) and 86 (switched). I will be using these once my wiring kit arrives.
volvo xc40 B4 mild hybrid
K9plus1
Posts: 27
Joined: Mon Nov 20, 2023 9:37 am

Post by K9plus1 »

I finished fitted my 70Mai M500 dashcam today. In the end i used:

VCC+ - Fuse 12 - Suspension module (this was a free slot for me) - Permanent Voltage
ACC - Fuse 83 - Interior lights etc. - Switched Voltage
GND - Fuse box fixing bolt (see below)

For some reason I couldn't use Fuse 86 for ACC, this was reading 11.8V on my voltmeter and was not registering on the dash cam. So swapped over to 83 which did the trick (12.2V). Had to move the existing fuse onto the piggy back.

The trickiest part was actually finding a suitable GROUND point as ALL the fixings around the fuse box are insulated (for good reason). On the left and right side of the fuse box, there is an insulated nut holding the fuse box to the chassis. If you undo this nut, it reveals a metal bolt underneath. It was a right pain to get a good connection here as wrapping the wire around this bolt was hit and miss (mostly miss) . Without a good Ground connection, the dash cam will not turn on! In the end, i had to put a metal washer over metal bolt to create a metal surface, wrap the exposed ground around the bolt and then re-apply the plastic nut over it to hold everything in place.

Also had to purchase 2 x piggy back fuse taps from amazon. https://www.amazon.co.uk/dp/B07Z4RWZSW? ... ct_details . You will need a crimp tool to connect the cables to the fuse taps. This little extra effort made trying different fuse positions 10x easier than trying to wrap around the leg of the fuse in a confined space!

Cables routed down the A pillar and behind the air bag curtain. Power cables tucked away and fuse box cover closes without issue. Watch https://www.youtube.com/watch?v=LHMjs0TDidg on how to remove the A-pillar cover. Once the bolt is removed, some force is required to pull it off. The other panels come off with relative ease. You will need to take off:

- A-pillar panel
- 10x45cm section just below it
- Side panel with the airbag switch (depress latch to disconnect the green connector)
- Side floor panel (you will need to remove the bonnet handle with a 6 point star screwdriver bit)

You will then have a free run to the fuse box.

Lesson learnt when putting the panels back together. DO NOT reinstate the A-pillar cover last. The panel about 10cm x 45cm long that runs vertically down alongside the door goes in last as it will need to overlap the A-pillar piece. Don't make the same mistake i did trying to shoehorn the A-pillar panel into the space and ended up scratching the dash surface.


Hope this helps.

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volvo xc40 B4 mild hybrid
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