Confused testing fuse slots with multimeter

whatwasmyname

Hello. I'm hoping someone can offer a bit of help here. 
I am looking to fit a dash cam which will require switched live as well as perm live & neg wires as I want to use the park mode feature which requires all 3 connected. The cam comes with its own hardwiring kit.

I looked up some videos on how to do it & set out to test, looking for empty slots first as I'd read these were preferable over tapping in to already occupied slots. 

I had about 5 unused slots. 2 showed perm live as reading 12v without the key in. So for the other 3 I put my key in, turned the ignition on but didn't start the car & went back to test the remaining 3 slots that were dead before. This time they gave a reading, but not 12v, they gave readings of 0.03v.

I don't understand as I expected it to read 12v at some stage, be it ignition on or ignition off. Could anyone explain please?

[Deleted User]

Sounds like those slots don't go live with the ignition. They might not be connected to anything, or relay switched or something.

You will have to try the occupied sockets.

facade

The usual way to add a circuit is to use a piggy back fuse adaptor.

These come in different types to match the different fuses.

You remove the fusebox cover, pull out a fuse that is live when you want, push this fuse into the lower position of the piggy back, then add a new fuse to the upper, and connect your device to the wire tail. (the fusebox cover then won't go back on, so you keep it in the glove box with all the other bits of trim that fall off and you can't be bothered refitting )

Contrary to some advice, these do have a right way round- the end that is common to both fuses goes to the live (feed) end of the fuseholder. They work the other way around, but then the current for the new device also passes through the original fuse. (You might actually want this situation though if the hair thin modern wires won't carry the rated current of both fuses added together without setting on fire)

whatwasmyname

facade said:

The usual way to add a circuit is to use a piggy back fuse adaptor.

These come in different types to match the different fuses.

This is the way I'm doing it. The kit I will be using is https://viofouk.co.uk/product/hk3-parking-hardwire-kit/ which comes with the required taps.

I know the cigar socket is switched live so that's the yellow one. Shouldn't be too hard to find a permanent live & there's various nearby bolts for ground. The thing is that I would rather use empty slots than already occupied slots and also that I want to hardwire a couple of other devices in there too. I'm not comfortable loading multiple devices up on one fuse. It may be ok to do so but I don't really know what I'm doing there but I'm ok enough to wire 1 wire to 1 fuse. 

So if the empty slots only read 0.03v when the ignition is on then would you just ignore that slot & move on to one that reads 12v when ignition is on (assuming it reads 0.00v when ignition is off)?

[Deleted User]

whatwasmyname said:

facade said:

The usual way to add a circuit is to use a piggy back fuse adaptor.

These come in different types to match the different fuses.

This is the way I'm doing it. The kit I will be using is https://viofouk.co.uk/product/hk3-parking-hardwire-kit/ which comes with the required taps.

I know the cigar socket is switched live so that's the yellow one. Shouldn't be too hard to find a permanent live & there's various nearby bolts for ground. The thing is that I would rather use empty slots than already occupied slots and also that I want to hardwire a couple of other devices in there too. I'm not comfortable loading multiple devices up on one fuse. It may be ok to do so but I don't really know what I'm doing there but I'm ok enough to wire 1 wire to 1 fuse. 

So if the empty slots only read 0.03v when the ignition is on then would you just ignore that slot & move on to one that reads 12v when ignition is on (assuming it reads 0.00v when ignition is off)?

Yes 0.03V is nothing, assume it's 0.00V. Anything suitable will be a solid 11V or more.

531063

Just connect both wires to the perm live.