The mystery of the blowing fuse

[Orchidius]

Hi there,

In an attempt to refit my floating oldtimer, I've redone all electrical wiring. I've also moved the battery and replaced all halogen bulbs by LED ones. Trying the system out for the first time last weekend, everything worked perfectly, except the cabin lighting... Flicking the switch on the control-panel, it blew the fuse instantly every time. I've been doing some testing, but can't wrap my head around it. I'm hoping you guys could shed some light on the matter (no pun intended ).

So here's the situation:

The control/fuse panel only has 1 switch/fuse for all the cabin lighting. Only one wire leaves the panel towards the center of the boat. There it goes into a (newly installed) box where the one wire is connected to about 4 separate wires going to the actual lightfixtures. This connection is made with https://www.google.be/search?q=wago+...15%3B720%3B533. All wires are new and there's both a positive and a negative wire for each lightfixture (not grounded to the hull).

Here's what I've done to test it so far:

1. Opened all lightfixtures and checked for corrosion or the like. It all seems really clean, but now that I'm writing this I realize I could/should have tested it with the multimeter to be sure.
2. Redone all connections and checked all wires
3. Ran the wire that comes from the control panel directly to one of the lightfixture, this works perfectly.
4. Used a different fuse/switch assembly on the controlpanel with the original setup, this still blew the fuse, so it's not a faulty part on the controlpanel.

A simplified drawing of the situation is attached. Does anybody know where best to look next? Apart from taking the multimeter to all the lightfixtures to double-check them, I'm clueless... The LED lights are 12V ones also used in cars, so no way 4 of these can blow a 10amp fuse...

[hellosailor]

Somewhere, there is probably a junction where you accidentally switched a hot wire for a ground wire, creating a direct short to ground, or there is a contact between a hot side of a fixture, etc. that is connecting to ground, which could be your hull.

You'll need to eyeball everything, or use a test light or meter to find it, but I'd bet there's a simple dead short someplace in there.

[Orchidius]

A metal screw tying the metal frame of the fixture to the metal hull wouldn't be an issue right, both being ground?

[FlyingCloud1937]

Start simple, remove all of the LED bulbs. Does it still blow the fuse?

If yes, undue all 4 of the junctions in the box, does it still blow the fuse?

If yes, it's a fault in the home run circuit, if no, it's one of the branch circuits.

Now put the LEDs back in their fixtures, then connect one at a time in the junction box.

Once the faulting branch circuit is determined, disconnect the light fixture, now ohm out the circuit wire, if no fault, then its the light fixture.

Lloyd

Originally Posted by Orchidius

Hi there,

In an attempt to refit my floating oldtimer, I've redone all electrical wiring. I've also moved the battery and replaced all halogen bulbs by LED ones. Trying the system out for the first time last weekend, everything worked perfectly, except the cabin lighting... Flicking the switch on the control-panel, it blew the fuse instantly every time. I've been doing some testing, but can't wrap my head around it. I'm hoping you guys could shed some light on the matter (no pun intended ).

So here's the situation:

The control/fuse panel only has 1 switch/fuse for all the cabin lighting. Only one wire leaves the panel towards the center of the boat. There it goes into a (newly installed) box where the one wire is connected to about 4 separate wires going to the actual lightfixtures. This connection is made with https://www.google.be/search?q=wago+...15%3B720%3B533. All wires are new and there's both a positive and a negative wire for each lightfixture (not grounded to the hull).

Here's what I've done to test it so far:

1. Opened all lightfixtures and checked for corrosion or the like. It all seems really clean, but now that I'm writing this I realize I could/should have tested it with the multimeter to be sure.
2. Redone all connections and checked all wires
3. Ran the wire that comes from the control panel directly to one of the lightfixture, this works perfectly.
4. Used a different fuse/switch assembly on the controlpanel with the original setup, this still blew the fuse, so it's not a faulty part on the controlpanel.

A simplified drawing of the situation is attached. Does anybody know where best to look next? Apart from taking the multimeter to all the lightfixtures to double-check them, I'm clueless... The LED lights are 12V ones also used in cars, so no way 4 of these can blow a 10amp fuse...

[Orchidius]

Good one, FlyingCloud. I had come to a very similar gameplan already myself, I guess I just needed to write it down to properly think it over again.

Thanks!

[westwinds]

I once had a short where the bulb fit into its socket.

[jkindredpdx]

Originally Posted by FlyingCloud1937

Start simple, remove all of the LED bulbs. Does it still blow the fuse?

If yes, undue all 4 of the junctions in the box, does it still blow the fuse?

If yes, it's a fault in the home run circuit, if no, it's one of the branch circuits.

Now put the LEDs back in their fixtures, then connect one at a time in the junction box.

Once the faulting branch circuit is determined, disconnect the light fixture, now ohm out the circuit wire, if no fault, then its the light fixture.

Lloyd

Right On!

[Ex-Calif]

There is a ton of "fuse blowing" complaints on the auto forums when converting to LED.

Unfortunately there is not much "root cause" identification and folks seem to have two theories - bad bulb and reverse polarity which doesn't make sense. Most fixes are basically changing bulbs until it works.

Also a lot of these guys have interesting theories about "low resistance" and are soldering in resistors, of course defeating the low energy feature of the LED - LOL... Auto mechanics - Sheesh!

Did you convert to LED at the same time as the wiring change?

The only LED related item that did make sense is one guy identified that he had "socket" type bulbs that could be inserted too far into the fixture causing the shell to short to the center (hot) conductor.

[hellosailor]

Dan, you got something there.

Some of the new LED bulbs have active components in the assembly, i.e. so they can be used with any polarity. Or dropping resistors or regulators or whatnot. And all of them are soldered onto some sort of carrier/board. So there are plenty of opportunities for a simple short circuit in the LED "assembly" and that's all it would take to blow a fuse.

Obviously, an opportunity for international terrorists to cleverly create blackouts and cripple the critical Satanic Global Recreational Marine Market. (sigh)

[FlyingCloud1937]

hellosailor,

That is exactly why I said start simple. While I have never seen quality LEDs cause a fault straight out of the box. I have replaced elder LED's causing a fault.

I have even had incandescent fail shorted.

Myself I would use my multimeter, for trouble shooting, but didn't want to get into the minutia of instructing on how to use the same.

Lloyd

Originally Posted by hellosailor

Dan, you got something there.

Some of the new LED bulbs have active components in the assembly, i.e. so they can be used with any polarity. Or dropping resistors or regulators or whatnot. And all of them are soldered onto some sort of carrier/board. So there are plenty of opportunities for a simple short circuit in the LED "assembly" and that's all it would take to blow a fuse.

Obviously, an opportunity for international terrorists to cleverly create blackouts and cripple the critical Satanic Global Recreational Marine Market. (sigh)

[hellosailor]

Lloyd-
I've never had a light bulb do damage out of the box, although I've had some burn out way before their time. LED "assemblies" snuck under my radar, I've never really considered that they might need to be suspected of anything. Then again, ever since I had one DOA new engine thermostat that left me pulling the engine head in search of "Why is this still overheating ?!" I've learned that "new" isn't always a perfect concept.

LEDs. Go figure.

Saw a PBS show the other night and found out the Confederacy was sabotaging Union steam boats with "coal torpedos". Basically, a small cannon ball cast to look like a lump of coal, mixed in with the coal pile on a riverboat. Stoke the engine and oops...one less riverboat.

Can't trust a light bulb, can't trust a lump of coal...Sheesh.

[Ex-Calif]

Originally Posted by hellosailor

<snip>
Then again, ever since I had one DOA new engine thermostat that left me pulling the engine head in search of "Why is this still overheating ?!" I've learned that "new" isn't always a perfect concept.

<snip>.

I had a Jeep Cherokee that would die on the road when it got warmed up. Definitely ignition.

Traced it to a $5 ignition system capacitor. Easy trip to AutoZone.

Didn't work.

Changed everything one at a time including a $300 computer.

Finally, bought another capacitor - all good. Painful and expensive lesson in troubleshooting and not relying on manufacturing quality. Difficult because the fault only showed up at high temp.

On topic - LEDs shorting in the socket would be tough to troubleshoot - All wiring good, stick the LED in, short... Hmmm New LED, short, new fuse, short, New LED, etc.

Continuity checks above and a continuity check with no power and LED installed might be an additional thought.