Connecting power via Central Fuse Panel

[CountOtto]

I've recently been fitting a brake controller to my D4 following some of the threads on how to get access to various points. While I was at it I was also going to use the power connection in the white 7 pin socket for my 15A fridge but discovered that the circuit had been derated from 30A (circuit diagram Fuse 46) to 15A which left nothing to spare. I decided to run another 6mm cable for the fridge and wasn't sure how to get through the firewall on the passenger side to access the battery without disassembling half the dash.
I noticed Repco had some Narva piggy-back fuse holders so I thought I would give them a try. The fuse holders are designed to replace an existing fuse, but as there are a number of vacant fuse positions on the D4 this would make them independent. They are a tight fit with no chance of rattling loose. I used fuse position 46 for the fridge and 28 for the brake controller. Attached is a photo.

[loanrangie]

Yep, handy little jiggers those fuse taps.

[Cambo_oldjaguar]

Just make sure you install them the right way around.

Because if they are the wrong way then the piggyback circuit won't actually be fused at all.

Seen a few meltdowns as a result of incorrect installation.

[John_D4]

Just make sure you install them the right way around.

Because if they are the wrong way then the piggyback circuit won't actually be fused at all.

Seen a few meltdowns as a result of incorrect installation.

How do you install them the wrong way? I have not used them but from the pic they look simple?

[Cambo_oldjaguar]

I was thinking “this would be a good topic for a video” and was going to make one myself.

But someone already did one.

How To Install A Fuse Tap & How It Works - Hardwire - YouTube (https://youtu.be/nasuPwpr55I'si=zUY3mDjH8B51u_Eh)

At around the 3min point he explains about which is the correct way around, so current flows through the 2nd fuse, not bypassing it.

[DiscoDB]

It is impossible to bypass the second (added fuse), but it is possible to install and end up feeding the new circuit through 2 fuses in series.

If installed in the reverse direction this combines the load on the original fuse - that is the original fuse would see both loads and could be overloaded.

https://uploads.tapatalk-cdn.com/20240105/f47f45232b9c127861758edb99d1d206.jpg

Installed as shown above and the original circuit and new circuit each get their own fuse fed from the 12V supply side - that is the new circuit bypasses the original fuse.

[Cambo_oldjaguar]

Not sure how that explains this kind of occurence...

188400

But I've seen it a few times now. Not ones that I've done but previous installs.

[DiscoJeffster]

Not sure how that explains this kind of occurence...

188400

But I've seen it a few times now. Not ones that I've done but previous installs.

I’m guessing it was installed backwards and the original fuse was doing all the work. I’d suggest the expander doesn’t have the heat sinking that the original box has through the frame/ bus bar and thus the current overheated the holder without being over current and blowing the fuse [emoji2373]

[DiscoDB]

Not sure how that explains this kind of occurence...

188400

But I've seen it a few times now. Not ones that I've done but previous installs.

If installed in the reverse direction, then probably too much continuous load now on the original fuse.

The other consideration with fuse taps is to make sure the supply side can handle the new combined load.

[BradC]

The other consideration with fuse taps is to make sure the supply side can handle the new combined load.

Also make sure the fuse tap can handle the current. Just because the source can do 40A doesn't mean you can whack 2 20A fuses in an add-a-fuse and have it last.
I've used a few of them, and not one I've looked at I'd trust over a gross 5A total. The contacts are too light/thin and it'd end up as a pile of bubbling plastic.

[DiscoJeffster]

Also make sure the fuse tap can handle the current. Just because the source can do 40A doesn't mean you can whack 2 20A fuses in an add-a-fuse and have it last.
I've used a few of them, and not one I've looked at I'd trust over a gross 5A total. The contacts are too light/thin and it'd end up as a pile of bubbling plastic.

Exactly. Like I said, the thing was overloaded.

[John_D4]

Thanks for explaining that Cameron. I hadn’t heard about them and I found that YouTube link quite educational.