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Hi all,

The alarm of my 2016 V40 (RHD UK market) R-design was going off at random intervals. An intermittent bonnet switch seemed to be the most likely cause, as it seems to be a common issue, despite the fact that the bonnet was correctly showing as open or closed on the dashboard display.

When I got access to the microswitch in the bonnet latch, I found that I could close the switch to the clicking point and the contacts would still have high resistance. The switch only showed properly closed when pressing hard beyond the clicking point, which is not normal.

I couldn't find any information on how to access or remove the switch, so here is an overview. The switch is located at the bottom of the passenger side latch (RHD car), the one close to the left headlamp (from the perspective of the driver). I removed the latch without removing the bumper, although the access is a bit tight, as follows:

1) Remove the left headlamp (2 bolts and a plastic locking cylinder, and with one plug to disconnect).
2) Disconnect and remove the disc horn (1 bolt).
3) Remove 4 bolts holding in the latch. 2 of these secure the secondary latch, which can be set aside.
4) Open up the plastic box that clips around the cable release connection, where it joins to the cable running inside the car. By separating the cable, the latch can then be lifted up to gain better access (don't close the bonnet while the cable is disconnected!)
5) Separate the latch mechanism from the lower plastic section, which just clips on.
6) Unclip and disconnect the sensor harness, which has an inline connector close by the cable connection.
7) Remove the hot melt glue under the microswitch, then bend the plastic tab and push the microswitch from below to release it. You will have to cut the wires to remove the switch.
8) Reinstallation is the reverse of removal!

The microswitch is a sealed lever type with dimensions 15x5x7mm, normally open. The Farnell part 2831795 might be suitable if the lever is cut down slightly. For the time being I simply soldered the bare wire ends together after removing the switch, and plugged the harness back in, so the bonnet always shows as closed. So far it seems to have solved the issue, as the alarm hasn't gone off since.

You might be able to bypass the switch without removing the latch, just by joining the pins of the open connector (after removing the headlamp for access), but be careful to tape it up to avoid water ingress.

The pictures below may help! The inline connector is attached to a white plastic clip and just slides off.
sensor1.jpg sensor2.jpg sensor3.jpg sensor4.jpg
 

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Brilliant write up, thanks
 
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