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Old 05-15-2022, 06:04 PM   #1
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Default Shore power works, battery tests ok, but no power in TT when on battery only

Our 2008 189FBR worked fine off battery power before putting it away for the winter (without the battery in it), but now it's changed its mind. Everything works as expected when the TT is plugged in to even just an extension cord from the house, and the battery tests fine (I tested and also took it in to a shop in case I was doing something wrong), but we get no power at all in the unit when it's on battery only (no lights, battery sensor panel doesn't register anything).

The inline fuse looked fine but I replaced it anyways, with no impact. I've checked with the cut-off toggle (in the forward storage area) pulled out and pushed in. No luck in either position. I also opened up the little cover in there where all the wires are crimped together and nothing looked wrong, but I haven't examined those connections carefully.

From what I've read so far, it looks like it could be due to corrosion on the battery leads (so I can try sanding them gently to remove whatever may be there) or potentially a place where the crimps have failed and the cable joins have come apart, so I can go through and check them a bit more systematically.

Not sure if there are more fuses beyond the inline one that would be impacting all power functions - when I'm at the trailer again I can check the fuse box and see if anything looks amiss there.

Just wanted to ask here in case there are other obvious steps I should be taking. I got a multimeter, but am a bit lost in terms of how to actually use it (both for settings and for just general knowledge about how electrical systems work), so I'm hoping to exhaust other more basic avenues first. Any suggestions?
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Old 05-15-2022, 07:16 PM   #2
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A continuity meter will help you find the break, if there is one. Those devices are not expensive.
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Old 05-18-2022, 07:22 PM   #3
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First off, make sure the master switch is turned on. Next, with shore power connected and battery disconnected, use a voltage meter to see if you are getting voltage through the disconnected battery terminals. If you are not getting any voltage, work up the line until you get a voltage. Issues could be corroded crimp connectors, bad fuse holder, broken wiring or bad converter.
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Old 05-18-2022, 09:37 PM   #4
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Thanks - that makes sense as a starting point. I test using the positive and negative connectors at the same time, right (not using the trailer frame to ground)?
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Old 05-19-2022, 05:36 PM   #5
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Yes, use the positive and negative terminal. As a double check, also use the positive terminal and frame.
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Old 05-22-2022, 11:21 AM   #6
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When you stated you changed the fuse did you mean the external fuse located near the battery? If so, the WFCO converter (normally used on FunFinders has one or two plug-in fuses located on the circuit board. The fusing at the converter is effectively in series with the fusing at the battery. This might be your problem. I imagine this means that your converter is not charging your battery. You should be able to determine where and what the fault is using a voltage meter. The WFCO website has manuals for their different models of converters. On mine there are two fuses located near the wire that connects power from the battery.
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Old 05-22-2022, 11:45 AM   #7
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Check the main battery disconnect switch, I had to replace my switch because it would be on but not make a connection causing the same problem you are having.
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Old 05-23-2022, 03:21 PM   #8
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Should the power at the leads be AC?
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Old 05-23-2022, 03:33 PM   #9
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Should the power at the leads be AC?
The voltage at the battery shut of switch is +12vdc on the HOT side and the other side of the switch connects to the light/fan/furnace circuits.

If you have two 12VDC batteries they are wired in parallel. If you have two 6VDC batteries they are wired in series. Either way the total voltage is 12VDC.
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Old 05-23-2022, 04:09 PM   #10
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Well, after more testing I have 4.8 mv at the circuit board... a long ways from the 12.3 v that it should be. Fuses all seem okay, so it looks like it might be the voltage converter. I'll try another battery first just to be sure...
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Old 05-23-2022, 04:50 PM   #11
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Well, after more testing I have 4.8 mv at the circuit board... a long ways from the 12.3 v that it should be. Fuses all seem okay, so it looks like it might be the voltage converter. I'll try another battery first just to be sure...
I'm not sure where you measured the 4.8 mv. Unplug the AC from the trailer. If you can touch the positive lead against the wire coming from the battery you should measure ~12VDC or the same as on the battery directly. After it goes through the fuse it should still be 12VDC. If you do not have the battery voltage on the lead going to the battery it could be either the battery cutoff switch (I do not know how your trailer is wired) or the wire between the battery plus and the converter may be broken.

I have seen the 12VDC supply in the converter (on mine it is mounted below the breaker and fuse panel) fail. Fortunately they are available as a serviceable assembly at RV supply stores and I have even seen them on Amazon. The trailer should have the battery voltage when it is unplugged even if the power supply is defective.
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Old 05-24-2022, 08:51 AM   #12
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I measured the feed to the battery on the panel, following the manual (remove the positive and negative wires, plug in to AC, then check the voltage). So, with AC plugged in I have nothing at the battery connectors, before the cutoff switch, or at the panel, which would seem to indicate that it's the converter, I think. Time to get it in to someone with more experience to make sure and get it fixed, though. I'll report back once I know for sure.
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Old 05-24-2022, 03:26 PM   #13
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That seems to indicate that the converter is malfunctioning on the DC side. With it plugged in to shore power, do you have any interior lights? If so, the converter is making 12 volt DC, just not connecting to the battery.
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Old 05-24-2022, 04:12 PM   #14
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That seems to indicate that the converter is malfunctioning on the DC side. With it plugged in to shore power, do you have any interior lights? If so, the converter is making 12 volt DC, just not connecting to the battery.
With shore power plugged in, everything works as expected (though, to be fair I didn't try AC this weekend), but without that nothing works... no lights or anything else. So maybe it is something between the converter and the battery? It's frustrating... I understand conceptually what needs to be happening, but don't know how to test for it properly with my multimeter, so I'm really floundering because of that.
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Old 05-24-2022, 09:44 PM   #15
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Maybe this video might help? It tells how to use the multimeter to test continuity.


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Old 05-25-2022, 07:49 AM   #16
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There is a company called Best Converter that you can call or email and get some help troubleshooting. Although they can sometimes be hard to get ahold of on the phone.
https://www.bestconverter.com/
If your converter is bad they can supply a replacement upgrade that is a drop in install into the power center. You most likely have WFCO converter which is notoriously bad. I went though this a few year ago and upgraded mine to a progressive dynamics converter from Best Converter.
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Old 06-10-2022, 10:09 AM   #17
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I have an update, kind of. Took it in to the shop and they spent 3 hours diagnosing and fixing it, told me my battery wasn't holding a full charge (which I knew, but which wasn't causing the problem) and fixed the problem. I asked what was wrong, and they didn't seem to be able to give me a straight answer... in the end, it seemed like the issue was the inline fuse on the cable going to the battery, which surprised me because I checked it and it appeared to be okay, but I replaced it anyways before taking it in. Then they told me a whole bunch of other things that they had checked, including the battery health (which I told them about when I brought it in) and two 40-amp fuses that I hadn't seen (maybe they could only be accessed by taking out the panel?).

I asked, if the inline fuse was the problem, and that was the first thing in the path from the battery, why they hadn't checked that first. They said they did check it first. I asked how that took 3 hours, then, and why they had to check all the other things... it almost seemed like they really had no idea what had actually caused the issue or fixed it. They reduced the bill a little bit, but the experience didn't exactly fill me with confidence about this shop, even though they had stellar reviews online, especially related to how honest they are.

I've since made a new friend in the neighbourhood... a guy down the street who's an electrical engineer and loves little projects like this, so he said next time just to call him and he'll help me figure it out. I'm hoping there's not a next time, but it will be good to have a new plan, in any case.
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Old 06-10-2022, 10:23 AM   #18
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On my WFCO Converter the two 40 Amp fuses are accessible without removing the panel. Have you gone to the WFCO website and entered your part number to view the information on your Converter?
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Old 06-10-2022, 12:15 PM   #19
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When I ran into similar issues, I discovered two problems at the battery. First, the in-line fuse holder (not the fuse) was bad. Second, the crimp connections at both the + and - terminals were corroded. I replaced the fuse holder, and cleaned the wire and replaced all the crimp connections. As added insurance, I than soldered all the crimps with electrical grade solder and covered them with heat shrink tubing. It's been 5 years now and everything still works.
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