Can someone please help me make sense of this?  -

'They're absolutely directional. If you don't orient the fuse tap properly, you'll be pulling both circuits off only one fuse.
To find the proper orientation, remove the original fuse from the vehicle fuse holder, and place the fuse for the new accessory in the fuse holder in the position parallel with the wire off the tap, and then re-insert the tap into the vehicle fuse box. Test with a DMM for voltage from the wire off the tap, and if you have ~+12V, you have it oriented correctly. If you don't have +12V, rotate the fuse holder in the fuse box, and then retest'.

 

I've found the fuses I want to use and have fuse taps fitted to the dash cam cables and fuses installed correctly in the tap - what I don't understand is how to work out which way up the fuse tap goes on the fuse box.. The above paragraph I found after a lot of searching and is as close as I've got to solving it. I'm assuming a DMM is a Multimeter, which I have. But I can't understand the next bit where it says 'Test with a DMM for voltage from the wire off the tap' .... Which wire?? there is only one wire coming off the tap and it's plastic! so I'm pretty sure you can't use a multimeter to check voltage on plastic? I have only tested fuses on the metal part. It's really frustrating to not be able to use my hardwire set up because of one missing bit of info regarding which way up to put the Fuse tap in the fuse box. Both fuses I've picked to tap into read 12v on both ends. I can literally finish the job in seconds when I know which way up to install them.

Directional is probably a strong word... They are very simple things.

 

Quick sketch:

 

So yes, it fitted 'upside down', both the circuit and new accessory will be drawing power through the original fuse. It 'could' cause nuisance tripping but given how much power a dash cam uses, it's quite unlikely to cause any issues.

 

 

If you remove the original fuse and the accessory still works, you got it right.

If you remove the original fuse and the accessory doesn't work, you got it wrong.

 

Simples

 

If you do want to use a multimeter, remove the original fuse and the tap, then see which of the fuse connectors on the board has 12v. That'll confirm which side is power...

 

Okay that makes sense, I was just worried about messing up my car electrics as I literally have no idea what I'm doing where electrics are concerned. I was confused by both fuses showing 12v on both sides but have now read I need to remove the fuse and test the socket with the multimeter. I will give it one more go tomorrow and remove original fuses as you said. Thankyou 👍

Reminds me to check mine. Maybe I'll do it tomorrow when I change the cabin filter.

My fuse tap will only fit the one way anyway, due to a larger fuse below. I'm only really checking for curiosity - it's been working fine for over a year in all conditions and loads.