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Car charger FUSE melted - WHY ??? Answered

Hi ... could someone explain me, why may car charger FUSE has been melted down ??? I was using it several times, and suddenly I realised, that it doesn't work. So I have inspected the fuse, and the wire in the middle was completely melted - a lot of small drops.

I have changed the use ... it worked 3 times and again. The next one as well.

Unfortunately I can't tell you, if it stops work when the charger is in the socket and I start the engine or by having the engine already running and then trying to put the charger in the socket.

I think, I did both of those situations ... but I'm not sure. But WHAT COULD CAUSE THE MELTING of the fuse, when before it was working OK ???

Thank you in advance, Zholy



You are all missing the clue. The fuse melted because the current passes through the spring behind the fuse and this acts like a heating element, anything more than about 3 amps and it glows red hot heating the fuse up and weakening it.

Pick a plug which is unfused or one where the spring is bypassed by the contact plate on the fuse.

The Electrial Gods are angry, and they demand SACRIFICE! Bring forth another FUSE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Fram has some very good points. The fuse is there to protect from any over-current conditions including damaged charger, wiring, or a short circuit. The fuse is a safety mechanism DESIGNED to melt so that nothing else does. If the fuse is blowing regularly, then somthing is broken.

Well... I would say that now it's regularly. But I have no idea, what could cause something like this to two different items. And I can't image, how over-current conditions could occur ???

Any component failure (could be not visible) or a shorted wire, or just a phsyical jolt can break the fuse enough to make it melt. Did you replace it with the correct size of fuse?

After melting the spare ones of each item ... I didn't replace them. I wanted to know what is causing it, (try to) fix it ... and then buy new set to give in the chargers

If you put the wrong size of replacement in, that would cause them to blow, otherwise its probably not user repairable.

You're either using to low a value for the fuse for the circuit, or you're drawing too much power, either by way of the device you've plugged into the port or by an internal short-circuit.

Why are you connecting the charger to the battery and then starting the engine?
This sounds stupid to me, but I'll guess your starter-motor-draw is "doing" the fuse. But you say that it happens with the engine started already, so just don't do that.


Are you replacing the fuse with proper amperage fuse that came out of the charger? Do not replace with oversize fuse either... that may cause wires to melt or other fire hazards. Could be your charger no longer has a good diode in it... or maybe you are connecting charger backwards to the battery.. You must connect PLUS to PLUS and MINUS to MINUS. (black is minus... RED is plus). If it plugs into cigarette lighter... then possibly your cig-lighter socket is backwards? It helps if you have a CHEAPY voltmeter. Get one at harbor freight tools for THREE BUCKS!!!! these meters are so cheap now that EVERYBODY should own one.

When it comes to replacing - I'm using 2 items (radio transmitter and my rear camera+screen). So far I was replacing the fuses with the spare one, tay came with the items. Now I don't have any fuses ... so I would like to understand, what causes the problem - so I could get fixed so I don't have to buy new fuses all the time The radio transmitter came with a spare fuse (the same as was inside when it arrived). I was using it several times ... and one day it stopped - the fuse has gone. So I have replaced the fuse with the spare one. I have used it 2-3 times and the same again. The rear camera&the screen are powered from the same source. I was using it for 4 months without any problems and now - BAF - gone. I have replaced the fuse, it worked 2 times and BAF again, the fuse has melted. I do have voltmeter - but I don't really know what to look for ??? How to check the over-current conditions, when it sometimes does work and sometimes doesn't ??? Thanks for any advise.