Need to find where 2-3 volts loss between full batteries and inside of 2023 T@b 320

kimch

I have been trying to resolve this for quite a while. I cannot get it into an RV place before a required upcoming trip, and the local mobile RV mechanic told me I've already done more than he would know how to do. I asked the Nucamp Owners Group FB page, but even Paul Thomas gave up and suggested I ask this group.

I'm going to copy and paste the thread from FB rather than trying to start from scratch to explain what the issue is and what I've done so far.

(Ignore my initial question in the FB post—my T@b has just the battery disconnect switch plus the three inline green fuses.)

Do T@bs (2023 320) have a 12 volt circuit breaker? If so, is it in the box between the front platform box and the camper (the box which the lines from the battery go through to get to the camper)? If not, what is in this box? (Please do not try to tell me circuit breakers are for 120. That's not what I'm talking about. At least some brands of campers have a 12 volt circuit breaker and I'm trying to confirm where mine may be before trying to open that box. And yes, I am aware of the inline green 30 amp fuses that serve, basically, to break circuits. I am not talking about those.)

Paul Thomas · The box you are looking at is the "junction box", where the connections between the 7 pin plug wiring, and the battery wiring, enter the trailer before being directed to the WFCO converter for 12V power, or to the trailer running lights. There is no "12V breaker", except for the the battery disconnect switch, or the 30 amp fuse at the battery. Turning off the battery switch will disconnect the 12V power from the battery "before" it reaches the junction box. To completely remove any chance of power at the junction box, you should also disconnect the 7 pin plug from the tow vehicle. What is it exactly are you trying to do? This thread has a discussion of what is inside the junction box, with pictures and drawings of the wiring at the junction box. https://tab-rv.vanillacommunity.com/.../junction-box...

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Barbara Warthen · Paul Thomas thanks. On a quick look at your link, it looks like the box has a bunch of connectors I should check for corrosion or looseness. (I can see that in a sealed box, things shouldn't corrode and hopefully not loosen, but I'm running out of things to check.) I'm trying to find where the lines are losing power between the new fully charged batteries and the camper interior. Two or more volts consistently. I've added an additional ground but that did nothing. And I've done tons of other troubleshooting and replacing, none of which found the problem.

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Paul Thomas · This is the link going to the drawing of the wiring inside the junction box. I'm not very skilled at this sort of thing, but the battery wiring from the battery disconnect switch should be easy to trace and check. It is also possible to have some sort of failure of the battery disconnect switch itself, either aging or corrosion. https://tab-rv.vanillacommunity.com/.../comment/128657/...

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Barbara Warthen · Paul Thomas actually, I was already planning to rewire the disconnect switch as soon as I have time. I replaced it a few months ago when the original died. Since then I’ve replaced and cleans a lot of connectors and such but if that isn’t secure, it could be causing the loss now that everything else seems clean and tight.

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Barbara Warthen · Paul Thomas I finally got to the disconnect switch today. It looked fine (everything tight, no corrosion), but I replaced the new one (a few months old) with the original one. The original had stopped working (no power in the camper) but it's working fine now. And I did get full voltage at each post. I have a new clamp meter but didn't find any amps loss with that today. I have ordered piercing probes but until I have those I don't know of any way to test the million wires under the seat for voltage. I did test every single ring connection at the battery and all show full voltage (I was careful to touch each connector, not the post), and of course the batteries show full voltage. I am at wits end as the probes won't come until to late for my upcoming required trip and I can't find any in local stores. Please suggest what else I can test for the possibly worsening voltage loss. Lately the camper has gone down to around 9.7 when the camper is still well over 12--so around a 3 volt loss.

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Paul Thomas · Barbara Warthen This sort of issue is way over my head, and I wouldn't have any idea of where to start. Are you a Tab Forum member? This is the kind of thing they are pretty good at, and there are plenty of resources that can help dig into the "million wires" you mention of the wiring harness under the seat near the WFCO. (There is info on what each wire is and the function).

Marceline

Where are you measuring the power in the camper?
What are your symptoms? (fridge not running? lights dimming? CO detector going off?)
I have a clamshell, and there's definitely a voltage drop between the battery and the 12v "cigarette lighter" socket all the way at the back, which I just always assumed was due to wiring length & gauge.

kimch

https://tab-rv.vanillacommunity.com/discussion/comment/223246#Comment_223246

Power at battery via multimeter, battery testers (that also show resistance, state of health, etc.) and Victron app. Power in camper via little plug-in 12 volt device that shows voltage, confirmed by looking at 1-4 lights on camper's battery monitor. Symptoms I already said. Power in camper was 2+ now is usually 3+ volts lower than batteries (2 new 12v batteries). Why a problem—Alde furnace won't kick on when camper reads in the 10s. (or lately, even around 9.7). I keep everything off so just have the small lights that can't be turned off drawing power though I have used the fridge a bit when full sun or when the batteries are on a plug-in battery charger at night. The camper is not in use right now—I am at home trying to resolve the voltage drop before a mandatory trip with the camper quite soon.

You said you always have a voltage drop. Of 3+ volts? And the monitor showing only one light when the batteries are full? That should not be normal.

Marceline

You said you always have a voltage drop. Of 3+ volts? And the monitor showing only one light when the batteries are full? That should not be normal.

Sorry if there was some misunderstanding. That's not what I said. I said that I've noticed a voltage drop at the back of the camper. I've never measured it. I noticed that it's enough that my electric cooler (separate from the fridge) doesn't work when I plug it into the 12v socket at the back (but does work when plugged into the trailer interior socket).

FWIW I have opened that box at the front of the trailer and it's simply a junction box. There's nothing in there but posts & wires unless NuCamp changed something and I can't see how adding an inaccessible breaker would be useful when there's already a fuse on that line from the battery. If you search this forum for "junction box" you might be able to find a wiring diagram for the junction box. I know that I had one at some point but I can't find it.

The only 12v breakers I'm aware of are the Gloso breakers in the solar system. I'm pretty sure everything else is just fuses unless someone modified your trailer.

There should be one main line going from battery into the converter inside the camper. From there the converter distributes 12v power throughout the camper. Have you been able to identify that one wire and test its voltage at the converter?

Have you noticed any weirdness with your exterior trailer lights (brake lights, turn signals)? A short or bad connection in one of those lines from the box to the light can cause mayhem. I once put a whole new wiring harness in a tow vehicle before I figured out that the problem was the boat trailer lights. Doh!

Grumpy_G

The way to track down voltage drop is with a voltmeter (doh ! 😀 ) but not by measuring voltage to ground but by measuring the actual voltage drop in the wiring section by section. E.g. you start at the battery and trace the wire to the first connection point. Measure voltage between those two points, it should read a very low voltage, ideally around 0.2 or less. The actual value depends on how long the wire run is and how much current is flowing through the wire. Do this section by section, you may need a piece of wire to reach between the test points if they are far apart. Note that this needs to be done for both the positive as well as the negative side (it's pretty common on older cars to have ground issues from rust).

Marceline

Wiring diagram someone made.

kimch

https://tab-rv.vanillacommunity.com/discussion/comment/223248#Comment_223248

Several white wires run between the camper and the batteries but I cannot figure out which is what. How do I find the main line you referred to?

I haven't noticed any light weirdness, but I really don't know what they do except when I test them before a trip then look at the side ones while driving when it's dark enough to see them.

kimch

https://tab-rv.vanillacommunity.com/discussion/comment/223249#Comment_223249

Interesting. That is new to me. I see what you're saying (I believe), but how do I test what I cannot see or reach where the lines all go into and come out of the camper? Or aren't accessible (e.g., to lights, fridge, etc.)?

Grumpy_G

https://tab-rv.vanillacommunity.com/discussion/comment/223252#Comment_223252

You don't have to test every wire, just between the battery and the "power center" a.k.a. fuse box because clearly anything connected there has low voltage issues (Alde, voltage display gizmo).

Actually it just occurred to me that I didn't ask the most important question: Do you have full 12V when the trailer is plugged into 120V ? If so it narrows the problem to the connection from the battery to the "power center".

kimch

https://tab-rv.vanillacommunity.com/discussion/comment/223253#Comment_223253

Great question! I've never plugged this camper into house power. I'll run some 120 tomorrow. It may be via an EcoFlow power pack, but 120 is 120 so that should work as well as an extension cord. I'll let you know.

TourDeForth

I haven’t seen this mentioned yet but as an aside have you considered the electric brakes? The brakes are powered when the battery switch is on. Probably not the issue but could be.

kimch

https://tab-rv.vanillacommunity.com/discussion/comment/223255#Comment_223255

How do you suggest i test this?

Grumpy_G

The trailer wheels would be locked up. Typically there's also a slight humming noise from the brakes, and the battery gets drawn down pretty quickly. It happens when the breakaway switch at the tongue gets pulled.

Seems unlikely to be the problem though because you would read lower voltage at the battery.

kimch

https://tab-rv.vanillacommunity.com/discussion/comment/223257#Comment_223257

No problem with the brakes last time I towed the camper.

Grumpy_G

Sorry I wasn't precise: The wheels would be locked up with the trailer just sitting, not connected to a tow vehicle. The breakaway switch would apply the brakes at full force.

FC1

kimch

Two separate topics related to voltage issue:

1. I decided to test resistance, as I replaced all the ring and Wago connectors at the battery, but that requires accessing two ends of a wire and the ring connectors either go to a Wago or go into the camper (i.e., disappear). Is there a way I can measure resistance of those wires?
2. More importantly, I have a new theory but need feedback. Behind the converter, about 1/2 dozen wires go into the DC side (I'm ignoring all DC lines). Right most is a slightly thick white one that goes to the left end of the terminal block. At the right end of the terminal is another similar white wire that's coming from the wall of the camper so I assume from the battery. I am betting these two are the main wires between the battery and converter. So first question is is that likely correct? I turned on the Alde furnace (sun is shining and the camper shows 11.0 volts which allows the Alde to work) and got .8 to 1. something amps on the right (incoming from battery) and only around .3 or so on the left one (into the converter). If I'm right about the wires, this is showing amperage drop. I can't figure how to test voltage until my piercing probes arrive. That all said, I think the few wires on the left side of the terminal block look awfully gunky. I am thinking I'll unscrew the left-most one, pull the wire and if it is corroded or otherwise gunky, cut, strip, and reinsert it. But I'd really like feedback from more experienced people before I mess around with the terminal block wires.

If I can figure how to post photos here, I'll post one or a few I just took in a bit.

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kimch