Fuse blowing instantly

[Stinger]

New to our 2014 1801FB, and new to winnieowners. Most of the 12v fuses are 20a, including the top 3 that service front, rear, and middle lights. The middle circuit blows a fuse instantly. I disconnected the 3 lights that wouldn’t turn on, and a new fuse still blows. 2 of the lights include the switch in the fixture plus an added switch like one in the bathroom mounted to the sink console, so that a person who couldn’t reach the overhead light could still turn it on. Also one close to the entry door that is a double, one for the outside light(s) and one for the inside entry light. A meter shows that one black lead to the lower bathroom switch is shorted to ground, while the other is not but does show continuity to the light above. As well, the black lead to the double switch near the entry door is shorted as well. Without a diagram I have no idea how to proceed to find the short.

[Morich]

This may be a tough one so, first note is to mention it may take time and dedication to find it. Starting out prepped for a tough fight can sometimes make it seem better???
But I can also say that it is not as high tech as many might think if we look at what is likely to happen. Sometimes electronics seems to be a total maze as there are lots of different ways to do the same thing.
But it is true that RV wiring is not too long, only as long as the RV and not super complex compared to many things we use, so we can start with what we do know and gradually add to it.

Sounds like you have the right ideas of chasing the problem and looking for where the power is going directly to ground. The basic idea of a "circuit" is that the power does have to get to ground to make it a full circle BUT we also know it has to go through the item we want powered to work right.

That means the power leaving the load center is finding ground before it goes through a light, so we can begin to use that and look at where that is most likely to happen. In a ways RV wiring helps us, even though it is small and lightweight, it is mostly single wires and that makes them far less prone to shorting to each other----except at special points where they have to come close together.

One of the most likely places for the power (hot?) wire to get to ground is where it goes through some type of metal. I could be worse and be some staple run through it but let's just not go there until we really need to???

So my first thought is that the load center has a good chance of being the problem as it often has a metal clamp of some sort holding the wires where they leave the back of the load center! But we may want to prove that is the correct guess and doing the proof is more difficult when we have to guess how the wires are routed.

My suggestion is to take a good look at the wire attachments where them come out of the back of the load center, if it can be done without major tearout, etc.
What type attachment does it have and is it a type that you might see grounding the hot lead?
When probing around there, look and sniff as if looking for a small burned area but also be careful to disconnect any 110AC source like cord and any inverter you might have on the RV. Then I like to go a step further and use something like a dowel to push and probe to move wires around, rather than a metal item that can add to my problems!

But, assuming you are not a super lucky guy, the short to ground may also be way out on any one of the wires away from the load center and that means you have to disconnect things until the short showing on the meter goes away.

Can you look at the trailer layout and think of running the shortest distance from load center to all the parts? It will take some guessing and maybe you can get sorta lucky by looking but there is a good chance you may have to go to most of the lights and switch, look to see the short is showing on the meter and then work your way along, disconnecting each item until we hope to find the short clears when we disconnect one wire. Did I mention this is not going to be quick and easy?

I suggest one way to avoid trauma is to start out assuming you will get interrupted while doing this, so use some form of tape or markings to let you be certain how to put it back together-----without having to "remember" too much of it! All those wires may begin to look alike after a bit, so mark them before taking them apart.

I would start at the load center, check that the first wire causes a short and take it off the load center, than work my way further and further out, hoping to find one that adds a direct short to ground when I put it on the circuit. Keep in mind that you will find places where there is contact to ground that shows a 100 ,200, or 1000 ohms to ground as that is the normal thing as power goes through different fixtures and to ground. The one you are looking for may be more like 10 ohms to ground.

[imnprsd]

Are you talking about 3-way switches?

If not and your fuse to a light is blowing, then my guess is that the spring loaded bayonet plug the bulb plugs into is the problem.

Fix

* Remove the light fixture.

* Cut out the wire to the fixture.

* See if your fuse blows. If it does NOT blow then you know you need to repair a frayed wire or replace the guts to that light fixture or buy a new light fixture.

Good luck hunting!

[Stinger]

Thanks! Not sure how to get behind or around the load center. Will figure it out.

[Stinger]

FYI, all light fixtures were disconnected and fuse still blows so it isn't as suggested. Regardless, thanks for the reply.

[Morich]

Totally agree on the problems figuring how to get to the right place on the converter! Part of why I do not suggest going with that first if it is too much!!
But if you really do need to go there, it may be true that getting the converter out is not as handy as getting the cabinet OFF the converter.
Whet I have found is that my cabinet is pretty much just Wood/paper, stapled together and if I work really careful, I can slide something like a tiny pry bar under one corner of the cabinet bottom and begin to tease the staples out to remove the section above the converter. I have to look at which section they put in last to find which may come out first---if that makes sense?
But getting the floor out of the space above was better than getting the converter out and let me see the backside where the wires comes out.
Replacing the "wood" was as simple as using a paper stapler (heavy duty _ to staple the edges back in place. Tempted to use glue but then I thought I might want to do it again and went with just staples like the first folks used!
My converter was metal and that left it more likely the wire had rubbed on it rather than the boxes as they are plastic?

But it can be a real bug hunt, so take a big cuppa coffee and settle in for the long haul. It really could be at the first place you look or it could be the one 22 spots down the line!

[Stinger]

I catch your drift but in this case I can't do that. The converter box is under the fridge. (heavy sigh). I am headed to take a look once again.

[Stinger]

The main wire from the circuit in question matches the wires in and out of the lower switch, yet checking that connection to ground is not shorted. (see enclosed pic)
Checking the positive post on the fuse holder to the the output wire is open while positive to other side is 12+V.
I don't know what that tells me.
Going to be away until Wednesday, then will check if the entire converter box can be slid out. Cover off, there are 4 screws securing the sides, and 2 on the bottom. Maybe...

[Morich]

I may be missing a little of what you are saying but I think I see it okay.
So let me do some guessing?

One is I think the picture got turned over? That happens a lot so I hope turning it over is right and what you are saying about the top three fuses looks better turned this way. Correct me if guessing wrong! That happens a lot, too!

So what I think I see is two big red wires bring power to the board, through the 40 amp fuses and I would guess the board then breaks it down to each 40 feeding about half the smaller fuses with wires going out to the right?
So the black wire second from top is the one where the fuse blows and you have it out. Can't see the third wire but we don't need to see it if it works okay!

But I did some drawing to show why you may be seeing ground when you look at the wire with a meter and it is correct, depending on how things are wired.

I might first take the black wire off at the screw where I marked with the blue arrow and then look for NO ground on the screw---just to make sure it is not right there at the load center, etc.

But when you look for ground on the black wire you may not see ground as you may be looking out along the wire like the green trail shows and seeing the path to ground open at switches, either before or after the bulbs.

But if there is a switch that is closed(turned on?) you may see ground as you are looking out along the red trail and back to ground.

I drew the bulbs at A and B as switches open but the one at C as closed, so I hope that makes some sense?

If you flip the switches at all the lights, the ground you are seeing may go away.

So we can kind of use how the power flows to get and idea of where the ground that is blowing the fuses is in the circuit, even though we have no idea of how the lights are actually wired, because we can't see the wires and don't have a drawing!!

The fuses blows because too much current flows and that is easy to see if the wire is touching/shorted to ground before it reaches the bulbs. It takes the easy "SHORT" path to ground and doesn't bother going through the bulbs to make them glow, too much resistance! We sometimes call it "power looking for ground" because it really wants to find it and takes the easy way to get there if it can!

If the wire is shorted to ground AFTER the bulbs, it doesn't blow the fuse because the amount of current flowing is limited by the resistance of the bulb and the big problem might be that we could not turn them off with the switch if the fault is in the right place.

In the last picture I drew what shorting to ground does in different locations as it makes a difference in how hard the power has to work to get to ground.
We want it to do the work of lighting the light and if it if shorted at the green arrow, we may never know it because that side is already connected to ground.
If the short is where the yellow arrow we can't remove the path to ground by opening the switch, so the light stays on.
If it is shorted at the orange arrow it blows but only when we flip that switch on.
But if it blows the fuse every time we connect the black wire to the screw and put the fuse in, we know it has to be shorted between the screw and the bulbs (red arrows) as it can get to ground too easy!

[Stinger]

Morich, despite what is labeled on the box cover, there is no output wire from the 3rd post, so the middle circuit and fuse are running 3 lights plus the outside light.
The 2nd post is not connected to ground as is, so I will disconnect that black wire, check post and wire for Gnd. Since that s/b part of the power to lights circuit, I could check continuity. Won't be until Thursday and I will print out your post and drawings to compare.

[Morich]

Since we don't get the actual drawings of the wiring for trailers, those are just examples of what "might" be how they wired things, so don't go put too much trust in them as being what you have!!!
Consider them as an illustration of how you may see ground if you look from the power center and a switch is on as it does often give a path through the bulb and switch to ground.
Point I was trying to make is that you may see ground looking at the wire leaving the load center but it should be a higher resistance reading if you are looking through the bulb and switch than if you are looking at a ground due to a fault in the wiring before it gets to the bulbs or switches?

What I meant was that you CAN get some info on where the short to ground might be if you look out on the black wire, reading resistance to ground when a switch is closed like in this top drawing and then the ground goes away when you open the switch so that the path to ground is opened.

But if you see a ground on the black wires, open the switch and the ground is still there, you can kind of guess that it is from the black wire being shorted to the ground at some point BEFORE it reaches the bulbs and switches.

The resistance reading on the top drawing here should be significantly higher than on the lower as it has to read the wire resistance plus the bulb and more wires?

Just meant as an example of how you might be able to use the readings and what difference the switches might make to help guess where the fault is located.

Not a really precise thing so that we can say it is some specific distance out like 4 feet or ten feet but just a way to get the best guess we have since we don't have drawings nor locations of the hidden wiring.

Not very good, but the best I see????

[Mtn Charlie]

Another factor that makes troubleshooting RV wireing shorts dificult to find is that manufacturers may use the same wiring harness in several different models to reduce part numbers and increase manufacturing quantity (reducing cost per unit). If the same harness is used in a 32 foot unit and a 36 foot unit, there could potentially be 4 feet of wire balled up somewhere. EDIT: That is an extreme example, but there could easily be several feet of excess wire. This came to my attention, when we had an open between two points. Winnie support told us there was a connector between those two points but had no idea where it was located.

[Stinger]

Morich: Put a meter on the #2 post to ground and got 10.8 ohms with black wire connected. Then checked from ground to a black wire at the bathroom sink - 11.4 ohms. Disconnected the main black wire from the #2 terminal. Red trouble light went out, and zero ohms from #2 to ground and black wire to ground. At the double switch by the door (for outside light and entry light) a small black wire that had been tack soldered to a + terminal on the switch was now broken loose from the switch Assy. When I pulled it out to have more room there is a label on the wire GND! This made no sense, but on a hunch I checked resistance to ground and got 11.8 ohms.
I don’t know what this tells me but looking at the wiring mess behind the double switch and under the radio/cd player would make one suspicious.

[Morich]

I need to check we are saying the same thing! When you say zero reading, do you actually mean you get a reading or do you mean the meter doesn't read at all meaning no path?
Zero would mean a really good ground right there but if you get no reading (infinite) it means all is good with no ground!
Since you say you get zero, I'm thinking you mean no reading!!! Same meter reading when touching the probes to things as when not touching them to anything?

A firm open/ no contact is what the meter says before touching the probes to anything but a solid ground is what the meter might show if you touch the probes together. Just wanting to avoid communications problems if we are speaking different!!

Sounds like the first test is reading the LED when connected and then when the wire is disconnected and you get zero to grnd, it is telling you the fuse mount, etc is okay and reading the wire only, it is okay.

A follow up question would be to check what you get reading the wire to grnd again but while you are getting a zero on the meter, if you try closing each switch at a time to see if one switch makes the reading jump up.
What we don't know is where the other end of that black wire goes first, so some guessing is needed but the idea is that as you close the switches, you will then expect to be reading like along the red line through one or more bulbs and to grnd to show up on your meter as a resistance reading ( might guess several hundred ohms) to reach ground.

Zero means you have no path to ground, while a reading is due to the path being there but some resistance due to reading through the bulb and switch.

Tell us more about the label at the door switch and whether it looks like there has been some work done? What type label, something stamped on the wire like factory or paper label, etc?
Sounds suspect as solder is not what I expect to find in RV factory work! Normal process doesn't usually switch the ground side but switches the hot side more often, so approach with care as you may be following somebody>>>>

[Stinger]

Firstly, I will check wire resistance with no fixtures on, then turn them on one at a time to see if I get an increase. Second, regarding the switch near the door: The label is AL wrap with block printing GND, very pro. Having it tack soldered to a + post made no sense. Besides, the crimp connectors for the switch are poorly done, so your comment about someone messing about is likely. I may need to look under the radio/CD as that looks crappy. Hope to find what needs to go to GND.

[Morich]

AARG!
Reason for thinking that the switch is more often on the hot side ,is that is more common in house wiring and carries over to many places in other uses like RV.

We more often find the white ground wire or "common" is just a bunch of white tied together and stuffed in the back of the box while the black hot lead often goes in and out of the switch. I've never asked why but it does make it easier/quicker if we want to work on the light, etc. if we can cut the hot side by simply turning off the switch instead of locating the breaker/fuse and turning it off. It never pays to trust it too far but in many cases it does work and is quicker.
I'm sure it's code but never questioned why????

[Stinger]

Richard, feel like I am spinning my wheels despite your help. To isolate easier in my brain, I am going to run a jumper wire from the #2 output post first to the lower bathroom switch post that is connected to the original output wire. If I tap the original wire to the post, I get a red light for circuit error, so if I get the same light after the jumper the short s/b between these two points.
Assuming no light, then run that same jumper to the dual switch near the door. Even getting a light there won’t tell all but progress.��

[Morich]

Yes, I'm also running low on ideas as the ground and positive don't really be things we want to touch !!
A tone to trace each wire while hidden in the walls would be nice but that doesn't work if they are connected together! You can get lots of info that the wires run in all kind of directions and that's what we already know.

Looking at what lights work and which switches might turn them on/off and then figuring a way to see if you can get wire to the ones which DON"T may be the best way.

One thing that is often true is that most problems do come from things at the fixtures, lights or switches and less often in the hidden parts of the wiring. So taking lots of those connections loose at each place may help clear some confusion.

NOT a good plan, though!

[Stinger]

At the camper now. Found by accident- with the center overhead light on and regular black wire connected to #2 lug, the red light is on. Turn off that light, the red warning light is off. There is a solid connection between the black feed line to the overhead light and the #2 lug, expected.
What should I know from this find?

[Morich]

I believe the red light is to serve to alert you the fuse is blown but how it does that is not one I've got into.

Anybody got info on what and how this red light at the fuse works? It was my pure guess that it was a way to indicate when a fuse was blown. Anybody got good info if that is true?

If you have a few extra fuses(???) one might try putting one in to see if the red light goes off and the ceiling light might work? Of course that risks blowing another fuse if there is a problem on that part of the wiring.

Do you know if that one light is controlled by that switch or does the switch also turn on other lights? If it controls more than one light, one way to cut the odds of blowing the fuse, would be to go into the wiring at that light and remove any wires that would go on to other lights.