Additional 6 way 12 volt fusebox

[Aigburth Lad]

All advice and guidance welcomed please -

Trying to get an added six way 12v fusebox (brand new) into my pals van to feed a couple of USB points and a couple of strips of LED lighting. Intention was to put each of the 2 USB's on separate fuses in the fuse box and same for the two lots of LED lights. 
Wired the new fuse box direct to battery and located same all nice and tidy inside the van with the main power cable protected at the battery with a fuse. 

First issue - I am getting power through the new fusebox out of each of the six terminals even though we've not put the fuses in the fuse box. Also, the small red LED indicator lights that 'marry' to each fuse come on if you load an accessory onto any of the six available slots - Is this right, I thought the Led's were to indicate a fault or blown fuse ??  

Second issue (sorry) we've intended to use those three terminal type switches that give you the function of a normal switch but with an illuminated LED when it's on. Problem I have is that the power on the accessory output is showing only as about 4.56 volts from the cable that's connected to the switch (less than 12" away). I'm using 21amp twin cable so should be ok or is that too heavy ? I'm suspecting either an earth/ground fault or maybe a fault in the new fusebox ?

Thanks for taking the time to read, any ideas please ?

[cancunia]

Sounds like a faulty fuse box. Any details on make / model?

[ffrenchie]

Disconnect the power and check for continuity across the fusebox with no fuses fitted. What kind of fusebox is it, does it have a busbar one side to supply power to all 6 fuses?

[Aigburth Lad]

Thanks for the replies, very much appreciated.
The fuse box is one that I have used before. It has a power input side with one main connect terminal for the link to the vehicle battery (via fuse) & six terminals for positive outputs to accessories in the vehicle. There are six holders for the individual fuses to be inserted for each of the outputs.
It then has a negative terminals block which I think they call a bus bar. Like the positive, it has a main terminal for the input and then feeds six negative/ground outputs.
I'm new to this and hope I'm not breaking rules but the link to the item I purchased is shown below.
I'm really grateful for the time and suggestions, that's what makes this forum so good.

https://www.ebay.co.uk/sch/i.html?_from=...1&_sacat=0

[cancunia]

No problems with posting links here so far as I know.

According to the listing, the red LED will come on when the fuse is blown, so it should probably also be on when there's no fuse. Maybe Zion will be along soon give some pointers.

[Gryffindor]

I agree with ffrenchie. The fuse box is probably faulty.

Do the LEDS come on when you have good fuses plugged in, or with no fuses plugged in? AFAIK they should only light if you have accessories connected but the fuses are no good (or possibly if they are absent).

Completely disconnect the fuse box from all wiring, then use a multimeter or a battery, bulb and 3 wires (can be a torch bulb and a 1.5v battery) to test continuity between all wiring connectors and all fuse spade connectors (i.e. pull the fuses out and touch your wire or meter probe to the spade receptacles at either end of each fuse bay, and the other wire.probe to other points).



Multimeter method
Put your multimeter on resistance setting. Touch any two fuse box contacts with the two probes. In general, for this sort of thing you can use them either way round; but because of the inbuilt LEDs it might be wise to play safe and only use the red probe on the + points and the black one elsewhere. The probes inject a small electrical charge and this might possibly damage the LED circuits if it is injected the wrong way round.

If you get no reading (infinite or maximum resistance) between two points, then there in no electrical connection between the two points you're testing. if you get some or no resistance (some or zero ohms), then there is an electrical connection.



Battery & bulb method.
Make up what is in the pic with a battery, bulb and some wire.

   

The battery and bulb can be any voltage up to 12v (or up to the fuse box max rating), but both the batt and bulb must have the same voltage rating as each other (though a bulb from a torch with say 2 batts would work work with 1 batt; it would just glow dimily). You can fix the wire ends to the bulb & battery with sticky tape.

LEDS probably won't work and may be destroyed. Use an ordinary glass bulb.

DO NOT DO THIS WITH MAINS ELECTRICITY!!!

First, check that the bulb and your wiring is okay by touching the two wires together. If the bulb lights, all is good.

Touch any two fuse box connectors with the two wire ends, again keeping the batt + wire to the + fuse box connections. Lit bulb = live connection, dead bulb = no connection.



What you are hoping to find is that one side of each fuse holder is electrically linked to the main [+] connector but the other side isn't. (The fault you describe suggests that both sides are.)

These other sides of the fuse holders should each be connected to one of the output [+] connectors but not to the others or to any other points.

Plus, the main [-] connector should be linked to all the other [-] connectors but nothing else.

If you get anything different, bin the fuse box.

[Sol]

Hi buddy, the unit in the link looks straight forward, battery + to the large terminal on its own at the bottom, ground to the large terminal on the neg busbar, then each load circuit goes to a fused terminal at the side and returns to one of the ground points on the busbar.

The LEDs are across each fuse in parallel, so if the fuse blows or is not inserted, the LED will come on. This is normal. A good fuse bridges out the LED so it doesn't light up when a load is connected and a good fuse is there. It shouldn't light if no load is present (no item connected to that fuse way) or the fuse is out or blown.

There's a series resistor on each LED that prevents it being damaged and limits the current through it when it's lit, but some loads like usb sockets or LED strip drivers may actually power on slightly due to the small current through the LEDs when the fuse is not inserted. If no fuse is in, you would see a small voltage at the load terminal of each circuit due to the led and it's resistor, now conducting. Take all measurements with a fuse in place.

This is why normal car fuse boxes don't have these "handy" LEDs, as they can cause weird effects when the fuse blows. May seem like a good idea to the Chinese designer but are actually a menace when fault finding.

Just check there is actual full battery voltage between the main ground terminal and main + terminal, and then from ground to each inserted fuse - the end of the fuse nearest the LEDs is the live end, but a good fuse will show a 12v live at each end when inserted even with no load connected. This is normal. A blown one will only be live at one end where the power goes into the fuse.

Then check each load terminal is the same voltage as the main battery, from ground. (With fuses in)

If all that is good, a standard 12v bulb should light up when connected between a load terminal and ground with the fuse in place, and go out when the fuse is pulled... With its associated led coming on if you then pull that fuse.

Small electronics items may still appear to power on because of the led circuit if the fuse is out, so be aware of that. If it was me, I'd cut out the connections to the LEDs if you can easily get to them. Use it was a normal fuse box is intended.

[Aigburth Lad]

Thanks Zion ( and others) - SORTED!!
One of the outgoing terminals on the negative side bus bar had a faulty connection where the outgoing cable (No 2) is connected. This was the negative side of the feed that registered only 4.56 volts when I was originally 'stumped'.
I should have done what Zion suggested which was to check all of them which would have flagged that one up as odd one out. Tightened up just a little more (holding breath in case I break it) and the whole thing then works perfectly. I couldn't possibly explain the technicalities but the LED's have also now sorted themselves out and light up if I put a u/s fuse in as suggested by earlier contributions. Who would be an auto spark ?!!
Thanks again, how good is this forum !

[Sol]

Glad it's sorted!