Fuseboxes with led warning lights


I wanted to alter the wiring, so pulled a fuse on the lighting circuit. One led spotlight still gave a weak pulsing light. I checked with a meter and there was a 4v reading at the light, even with the fuse out?
The wiring and joints were all good and the light went out when I isolated the 12v hab electrics.
Any ideas what causes this?
Chris; is there a negative return wire running back to the fusebox?



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In my last van I had 3 x the same same fuse boards. One of them did the same on 3 of the fuses (light stayed on or was faded).

I swapped it for another and problem solved - was a faulty fuse board.

In next van I've swapped all 12v fuses for breakers. More for neatness, but should be more reliable (and instead of a LED I'll see a MCB tripped)

As said, no earth, so these fuseboxes with the LED indicators, while very handy, can only tell you when a fuse is blown on an circuit with a load on it (as that is how it completes the circuit).
So for example, if the circuit is for a 12V accessory socket, the light will not come on if the fuse is blow UNLESS a device is plugged into the socket (This could be important to know if a 12V device is plugged in, doesn't work and you unplug the device before checking for a light).

So, is it always best to have a definitive earth? .............. My entire system is somewhat over the top as I have mostly used 2.5mm cable, with every single device having a return to a central earthing post.


So, is it always best to have a definitive earth? .............. My entire system is somewhat over the top as I have mostly used 2.5mm cable, with every single device having a return to a central earthing post.
There is no earthing point on the fusebox.
There is no earthing point on the fusebox.
Chris, there isn't an earthing point on my fusebox either, but the way I have installed my system (which I agree was OTT), I mainly used 3 core 2.5mm EHU cable for even the lightest load itemeven if they only needed a 1 or 2 core supply and in all cases I ran a earth from the device back to the large centralised earthing post in the electricity cupboard.
The question about an earthing point on the Fusebox was initiated (I think) by the fact that there are LEDs on the fusebox and how can the LEDs work with no earth. On that point, the earth for the LED is via the cable AND device the fuse is protecting.

In terms of Earths - or actually Chassis Grounds as they should be termed, so will use that term from now on - there are multiple ways to go and each have their own benefits and cons, and fans or otherwise.

Localised Grounds: This would typically be running a +12V power cable from fused supply (be it battery or fusebox) to devices and then running a 0V/GND cable from device to a local metal point on the chassis.
PRO: Reduced cable cost; Reduced Weight
CON: Potential issue with random poor earth connections means hassles if needing to troubleshoot

Centralised Ground: This would be running typically dual core cable from supply to device, carrying both +12V and GND cables, so providing a central +12V power AND a central Ground
PRO: Simplied Central Ground means simplied troubleshooting
CON: Increased cable cost as doubling up on length of every +12V cable while saving on the short lengths of 0V/GND cables; Subsequent increased weight; Routing cables can be harder depending on amont of cables and space

On the face of it, the centralised ground would seem to be the better option, but if care is taken when using localised grounds that localised Ground approach is just as good on a metal framed vehicle (talking road vehicles here - boats are a totally separate thing before words like "galvanic corrosion" start appearing).

Personally, I tend to use localised grounding just like the OEM vehicle electrics use. You don't see Ford, Mercedes, VAG, PSA, et al runing all their circuit grounds back to a centralised point as the vehicle monocoque IS the chassis ground. There is no reason whatsoever not to take the same approach with Leisure Electrics as was done with the Vehicle Electrics.
The last design I did interestingly enough is, however, using a central design with twin core (+12V + GND) cable to the 12V devices dotted around the vehicle as I was not sure if the installer would select the right ground points so decided to eliminate that risk (so every circuits 0V/GND is terminated in a single area).

Phil, personally I think you using 2.5mm arctic cable for eveything was not a wise idea. Not only are you using excessive cable in terms of weight (you have 3 cores when at the most only 2 was needed, so an immediate 50% extra weight incurred, plus the extra heavy outer insulation on top), and the extra cost over two-core cable, you have a cable that looks like mains cables but is carrying a ELV 12V circuit.
This is fine until someone sees a run of blue arctic cable and assumes it is more 12V DC cable (as that is the standard used) but is actually 240V AC cable. I know people do this as they have the cable spare, etc and why waste it, etc, but I feel it is very poor practice (sorry :( ) and should be discouraged - maybe the converter knows what cable is what when they installed it, but memories fade, and vans move on to new owners and using the albeit fairly rough standardised approach as much as possible when it comes to wiring really should be done where possible.


On my current van, I used a centralised connection like this (with cover)
neg conn.jpg

After trying to find earth faults on caravans, trailers etc., I much prefer to have all the negatives in one place.

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