Half power to some 12volt circuits

[GaryT]

2020 Winnie Outlook 22c
Rear bedroom pullout only

On recent upgrade of a switch to the two bedroom ceiling led lights, I touched the plus and minus terminals together for a second.
The result has been that now these led ceiling lights now only have 7.4 volts going to them. In addition the bathroom light also, only has half voltage to it.
I've check all the fuses, and all are ok and I have no idea where 12 volt to this area comes from. All other 12 volt lights work normally.
Connected or disconnected to shore power makes no difference.
Not sure what to check next. I was thinking connecting a 12 volt supply to each light to make sure they fully illuminate. Could one of the lights be keeping it from getting the full 12v supply?
The light switch only has one side of 12volt (yellow)
Lights have both plus and minus lines attached (black and white)
Any ideas appreciated.

[Morich]

some questions and then some thoughts on what I might do. Can you tell us more about what you mean the switch only has one side of 12 volt? When you test with meter one side shows 12 volt but not the other? I assume there are two wires on the switch? How are you placing the probes when testing and is this with the switch on or off? If you have the meter with one probe on a known good ground and the other touching first one side of the switch and then the other, it should show 12 volt one side only when turned off but both sides when turned on.
since the switch is what you were changing, that might be a place to start to make sure it is not causing a problem.
What type LED is this, a bulb that can be pulled out or the type which is soldered in and not meant to be changed? If simple bulbs to pull, try removing them to check but I would not expect it to be the problem if that type bulb. If pulling bulbs, make sure to note which way it is turned as they are polarity sensitive and have to be turned the right way to light. Easier to mark than to guess when putting them back.

[Goodspike]

My guess would be a measurement error, possibly due to a poor connection on the points you're using for your tester. Or if it's a digital tester, maybe its internal battery is going bad (but then other 12 volt circuits would probably give odd readings too). Are the lights seemingly working fine?

The other possibility would be that you damaged the fuse such that it connections were damaged, but I think that's extremely unlikely. You might though try reseating the fuse and/or switching it out with another of the same size. I think that's an extreme longshot.

[GaryT]

Thanks for your replies.
To be more specific

The switch only has one wire running thru it (yellow) to lights.
I did not measure current here, but at the termials of the LED lights.
These lights are a group of LEDs on a curcuit board. They all light but very dim now.
Imeasured the current here at the b/w terminals.
The fuses on the power control have a light that comes on of the fuse is bad or if you pull.the fuse. Checked these and all seem good.
Current was measured with digital meter.
The switch was wirking fine. I was trying to upgrade it to a dimmer switch when i acidentally shorted.the line when plus and minus terminals touched. I had run a 12v line fom another wire. At this point the dimmer switch also shorted out so i placed the original switch back in line.

I did this upgrade on the main light switch of he RV without incident.

[Goodspike]

I think you need to do this sequentially, starting first with changing the battery on your digital tester if it is more than a few months old (or could have been left on accidentally), although if the LEDs are dim, something is wrong somewhere, but at least there would be no question about the tester.

Measure the current at the light switch to a good ground. If that is not okay, the problem is before that point in the system, perhaps the fuse box as mentioned before. But whatever it is, it would be before that point. If that voltage at the switch is okay, then take the light switch out of the equation by removing it (connecting the wires together at the switch location) and testing the light output and current at the wire to the light (not the terminal and again with a good ground). If those are fine then the problem is likely the switch or the ground of the circuit (possibly due to your work having pulled on a connector further down the circuit).

Oh, and obviously make liberal use of the battery disconnect before you work on disconnecting and reconnecting the wires. You don't want to accidentally touch something to something else a second time.

[Morich]

Getting a better picture, I see we may not be speaking quite the same, so needed to check.
One thing to first question is if you have found the type fixture and LED are made to be dimmed? Some LED can be, some can't and the new ones for Rv, are not something I've worked with, so a point to check.
Small point on terms is that we are looking at the voltage, not the current. No big thing as I know what you were testing. If we were speaking of water, voltage is how much pressure, while current is how many gallons are running past. Like I said, no big thing as long as we are getting the idea across.
One the switch, I assume there is one yellow wire coming into the switch and that should have 12 Volts, then the switch has to close to let the power run out the other wire from the switch and that side should have 12 volts showing on it.
Does that sounds like the switch you have? There are always new things and it's possible, you might have a new type switch that I've not seen before.
If this sounds right on the switch, I might ask about the lights. Are they connected so that you could take a ire off them and see what the voltage is then or are they "hard wired" so that one would have to cut wires to do that?
Often the lights have a set of wires in the ceiling but when we look at the light, it is a different wire because they have made a connection just a few inches away from the light and tucked the connectors up in the ceiling! Maybe pulling kind of gently will get those connectors to come out of the ceiling or whereever they may have hidden them?
My thought is that we need to check there is good 12volt power getting to the switch, then getting through as we turn the switch on and finally getting the power to the light. The problem is that the light might have a problem and looking at a point on the board may not be telling us the right story, so it would be nice to know for sure by taking the light off the wires so that any problem in the light is not going to bother the testing.
Could be a defective light or might also be that we are not measuring at the right spot on the light as this type LED fixture has to have some "gizmos" that an old light does not. The 7 volts may be correct for that point on that board???

[Goodspike]

Originally Posted by Morich

Could be a defective light or might also be that we are not measuring at the right spot on the light as this type LED fixture has to have some "gizmos" that an old light does not. The 7 volts may be correct for that point on that board???

That last point is a good point. I wouldn't be measuring off the light itself, but instead the wire if possible.

I'll throw out another possibility--if a new light perhaps it was installed backwards. I would think that would result in no light at all instead of dim light, so another unlikely scenario, but worth testing that the proper wire was connected to the proper side of the light.

[GaryT]

Ok, thanks guys. This gives me some process to continue the problem solving process. Today i will see what other information develops from testing and disconnecting lines.
Thanks for all your suggestions. Will follow up with results.

[Morich]

Another small point that might be helpful is the way they now try to ID the wires. This is a link to the wire ID chart and it may help:
https://www.winnebagoind.com/diagram...ical_guide.pdf
Theory is that we should be able to look back along the wire, spot the code of 1-3 letters printed on the wire and then use this chart to find two columns listing one "from" and to the right a column of "to" and then we are supposed to know where that wire goes! Kinda helps if we know what the abbreviated description means and actually WHERE that item is located!
Could be called hunting and pecking through the forest? Good luck and keep us posted as time allows.

[Wyatt]

At first I thought you damaged the dimmer when it shorted, but you put the old SPST switch back. So assuming that switch is good, (I would check it with an ohm meter out of the circuit), And I like the idea of just twisting the two switch wires together, which effectively takes the switch out of the troubleshooting loop.
Now, if you do that and the lights remain dim, it’s not the switch, as mentioned.
But what if when you shorted the wires, you damaged the FIRST LED Light in the loop, and it now has excessive resistance, lowering the voltage to the other downstream lights.
Once you know it’s not the switch, each light must be checked for voltage on both sides—coming in and going out to the next light, as they are almost always wired in series, not parallel.

[Goodspike]

Originally Posted by Wyatt

But what if when you shorted the wires, you damaged the FIRST LED Light in the loop, and it now has excessive resistance, lowering the voltage to the other downstream lights.

How about this? If the two lights were incorrectly connected in series that could cause issues.

When I bought my house the main bath downstairs had three electrical issues, one of which was the fan running in series through a 60 watt bulb.

[Morich]

Originally Posted by Wyatt

At first I thought you damaged the dimmer when it shorted, but you put the old SPST switch back. So assuming that switch is good, (I would check it with an ohm meter out of the circuit), And I like the idea of just twisting the two switch wires together, which effectively takes the switch out of the troubleshooting loop.
Now, if you do that and the lights remain dim, it’s not the switch, as mentioned.
But what if when you shorted the wires, you damaged the FIRST LED Light in the loop, and it now has excessive resistance, lowering the voltage to the other downstream lights.
Once you know it’s not the switch, each light must be checked for voltage on both sides—coming in and going out to the next light.

This is where not knowing how the fixture is built is a problem as LED are a lot different than other lights in the way they work when burned out. Some are wired together in a string (series) and when one burns out they all go out but that is a pretty cheap way to go-- for that reason. LED is the big rage in aquarium lighting and it is always a question how they set them up as each LED needs a specific amount of current to both light and not burn out. Parallel is more common but there are lots of different ways to get the right current to each LED. So it depends on the design whether burning out one LED on a group will make it go dim, go bright, or what. Some are set up so that one damaged LED stops using current and that leaves more for the remaining and they get brighter, up to the point they begin to pop one after the other.
Low voltage is a bit harder to explain why than total loss.
Does need some checking, for sure.

[Wyatt]

Originally Posted by Goodspike

How about this? If the two lights were incorrectly connected in series that could cause issues.:

I agree, but from what I’ve read, his lights worked fine until he shorted the switch. Unless, he also played around with the lights while troubleshooting and put a light back wrong?

[Goodspike]

Originally Posted by Wyatt

I agree, but from what I’ve read, his lights worked fine until he shorted the switch. Unless, he also played around with the lights while troubleshooting and put a light back wrong?

I was thinking more this was all one project, so I'm not sure it ever was working right. Maybe the OP will shed some light on that (pun intended).

[GaryT]

Alright, took some time today. pulled the lights to take a look and got nowhere.
Disconnected shore power, Had converter off, still had dim lights till I switched battery off. At that point no power to lights.
Took another look at the control panel (with fuses). They make it so easy to get to. Had to lay down on floor with flashlight, and low and behold the top most 15amp fuse was blown. I did not notice it at first because it is slightly up under the cutout and the OPEN circuit light (a red led) was dimmer then the others that came on when I pulled other fuses.
So I replaced the fuse, and presto, both the two ceiling lights in bedroom and single bathroom led work at full brightness now.
I still do not understand why I would be getting partial power to the fixtures if the fuse was blown.
Thank you all for the suggestions on what to check for and your electrical knowledge.
Spurred me on to not give up.

[Goodspike]

Glad it's solved, but there's still the mystery of WTF happened! Very strange given the solution was seemingly something I described in my first post as extremely unlikely and an extreme longshot.

[GaryT]

Wyatt you are correct. I did not mess or replace the existing ceiling lights. I was just replacing the on/off switch with a dimmer switch. The dimmer requires a ground wire for it to operate, and that is when I accidentally touched the two. Apparently both blowing fuse and the dimmer switch. I then just put the original switch back in line.
PS- I had replaced an on/off switch with similar dimmer switch in the main coach area with no problem. Same type switch and ceiling lights.

[Morich]

At this point there is no way to say what has happened but I suspect there is a flaw in testing somewhere or some detail that we are missing. I have never seen a blown fuse leave voltage on the line. The fuse would not have much value if it doesn't remove the power from a defective circuit. All fuses I've seen are either good or bad, no in between.

[Goodspike]

Originally Posted by Morich

At this point there is no way to say what has happened but I suspect there is a flaw in testing somewhere or some detail that we are missing. I have never seen a blown fuse leave voltage on the line. The fuse would not have much value if it doesn't remove the power from a defective circuit. All fuses I've seen are either good or bad, no in between.

I would tend to agree, but when I raised the idea initially I was thinking of the connection with the fuse having gone bad somehow. But if it were only a second of extra heat, I just don't see that happening.

But yeah, if you're just testing voltage even a strand of wire would give you a 12 volt reading, so it probably wasn't the fuse itself (as opposed to its connection).

[NormD]

From the description is sounds like the bedroom and bathroom lights all run off the same fuse. The difficulty diagnosing the blown fuse appears to be a “ghost” connection to some other circuit. That strand of wire Goodspike suggests could be in the fuse panel or elsewhere in the wiring system and is likely next to impossible to find without a lot of work. Best to document it for future information and go on with life.


My question is if the dimmer switch is really damaged. Apparently, the dimmer modification worked well elsewhere, but the dimmer switch was not tried after the fuse problem was resolved and 12 volts was restored. Is that true? Perhaps the dimmer is still okay and will work as intended.