Basic electrics question re fuse box.

[FairweatherDave]

Got a little fuse box with 4 blade fuses in supplied by a single positive. If a fuse blows a little red led should glow to indicate which fuse has gone. I thought I would see what the voltage was, from one of the output terminals and got a nice 12.2 volts. Then I removed the fuse and still got 10v, which I wasn't expecting. Then a bit of reading suggested that there will still be some current to allow the red light to indicate a fault. Is my little fuse box working properly? Any advice much appreciated.
This is a link to the fuse box.....
Standard Blade Fuse Box With Positive Busbar & LEDs - 4 Way

 

[Aurai]

Hi, supposing you used a multi-meter, try the amps setting across the terminals, with and without a fuse in place. I suspect voltage may not drop much, as it needs enough to light the faulty bulb. However, amps should be higher with fuse in place and lower without?

 

[wonkywinch]

Hi, supposing you used a multi-meter, try the amps setting across the terminals, with and without a fuse in place. I suspect voltage may not drop much, as it needs enough to light the faulty bulb. However, amps should be higher with fuse in place and lower without?

Please DO NOT DO THIS. It is incorrect advice and will lead to a broken multimeter and/or blown fuses.

OP - is there any load connected to your fused outputs when you are testing? A normal load would pull the terminal down close to 0v if the fuse blows.

Without a load, you are just seeing some forward voltage though the LED.

 

[FairweatherDave]

Please DO NOT DO THIS. It is incorrect advice and will lead to a broken multimeter and/or blown fuses.

OP - is there any load connected to your fused outputs when you are testing? A normal load would pull the terminal down close to 0v if the fuse blows.

Without a load, you are just seeing some forward voltage though the LED.

No load on the terminal.

 

[wonkywinch]

Then put a small load on it, I use a car indicator bulb with a couple of wires soldered to it for such things.

Then you'll see it function correctly.

As a heads up, your linked page does actually state:

Please note that in order for the red LED to light, a very small, limited current passes through the circuit so you may still register continuity across the fusebox terminals when a fuse is blown or no fuse is in place. This limited current is completely safe but may cause connected LED lights to glow faintly (since they require such low current to operate).

 

[FairweatherDave]

Thanks WW. Yes I read that later re my fuse box. Will try a test with a load. I think I did a continuity test with the meter which was positive which did surprise me. It does sound like things are fine.

 

[wonkywinch]

Thanks WW. Yes I read that later re my fuse box. Will try a test with a load. I think I did a continuity test with the meter which was positive which did surprise me. It does sound like things are fine.

If your multimeter has a diode test function, then, with the fuses out, test across each circuit (common in to each of the four outputs). The meter will read (or beep) with the probes one way round but not the other. This is because a diode (even the light emitting variety) are basic semi conductors. They'll conduct electricity one way but not the other.

Diode function is at 5 O'clock on this model, looks like an arrow touching a bar (electronic symbol for a diode).