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Old 08-05-2018, 08:59 PM   #1
Bierp
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Loss of 12v power and questions on self resetting breakers

Need some help, please.

My new 3950BR has had the intermittent breaker issue with the slides and jacks since we got it in June. Works fine on shore power, but has interruptions on battery. It's a new unit and we've been on a really hectic schedule, so this has been on the back burner a bit. I've been hooking up shore power before doing jacks and slides and that's been fine.

Today, however, things took a turn. We did a stop while driving and I went in to the rig to find out that I had no 12v power at all. This was disconcerting and I'm still trying to figure it out.

Some background. Unit has 4 6v batteries and a 2000w inverter. While the 12v system was offline, the 120v system was working via the inverter. That means I didn't lose battery power, but something in the line isn't behaving nicely.

I did a CAT scale weighing yesterday which required me to use the front jacks on 12v. That's the first time I've done that in a few weeks. The 'break' it had was pretty long, but it did come back online eventually. I think that was probably a sign of trouble though.

Looking at how it's setup, I seem to have two self-resetting breakers in series. I'm posting the picture so someone who knows electricity better than I (and that could be nearly anyone, though I am getting better) can tell me if I'm correct about this.

With the rubber covers on, I can't see the rating on the breakers and as you can see, there's a lot going on there, so I'm a little reluctant to start uncorking things.



I put my meter on the battery that has the primary leads and I was over 6v. I take that as further proof that the batteries aren't the issue. Combinations of the breakers seemed to be all over the place, but I didn't find a combination that was consistently over 2v, which seems problematic. I did this just before dinner and we were on shore power, but I wouldn't think that would matter at that point in the circuit. (Though maybe it does because it wasn't in use?)

If one of those breakers went completely kaput, I'd experience this kind of total 12v failure, right? But the inverter would still have a viable battery draw to power the 120 systems, right?

Further points. In the battery compartment I have 3 in-line blade fuses. 30a (for the jacks I think), 10a and 5a, which do something, but I don't know what. (I was tinkering with those while sweating to death in a rest area.) All three appear to be intact, though I didn't actually test them on the meter.

So, understanding that my electrical skills are nominal, am I approaching this correctly and am I right in thinking that the self-resetting breakers are likely the problem? Is there a test I should run with my meter? (If you say that I should check something behind my converter breaker panel, I might freak out...but say it anyway if it's right.)

If I replace the breakers, considering that they're in series, what amperage should I get? Two 80a or two 40a or...?

Any pointers here would be most appreciated.


Thanks,
Jeremy
 
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Old 08-05-2018, 09:14 PM   #2
Carl n Susan
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I am not going to be much help here with the loss of 12V power. But I can tell you the two self-resetting breakers are paralleled. The battery feeds both at the same time. The second breaker doesn't depend on the first breaker operating to supply power.

Replacing the breaker that feeds the hydraulic pump is all that is required. The other one should be fine. There is a copy of the Lippert Tip Sheet about the undersized breaker in the Files section.
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Old 08-05-2018, 10:04 PM   #3
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Every time you operate the jacks, you are operating them with 12 volts, because they are directly connected to the batteries. The breaker that is wired between the batteries and the hydraulic pump is the one that should be replaced with an 80 amp breaker, either a manual reset or an auto reset. The photo shows a manual reset that I installed in our rig.
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Old 08-05-2018, 11:53 PM   #4
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Quote:
Originally Posted by rohrmann View Post
Every time you operate the jacks, you are operating them with 12 volts, because they are directly connected to the batteries. The breaker that is wired between the batteries and the hydraulic pump is the one that should be replaced with an 80 amp breaker, either a manual reset or an auto reset. The photo shows a manual reset that I installed in our rig.
Ok.

But is there any possible/probably correlation between that specific breaker and my full loss of 12v? Is there a specific way to test this on my meter?

I'll definitely replace the breaker for the hydraulic system, but if I still can't turn a light on without shore power, I've got more issues to resolve. (This is a fairly common occurrence when I start 'fixing' things.)

CnS, thanks for the Lippert doc.


J
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Old 08-06-2018, 08:59 AM   #5
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Mine is older, but I do have two auto reset circuit breakers. One feeds the hydraulic pump only. The other feeds everything else in the trailer, apparently, as the wire disappears into the wall. So tripping the breaker for the pump would not cause a total loss of power to the trailer on mine. Tripping of the other breaker, I assume, would.

Using a voltmeter, measure the voltage on each of the circuit breakers. You should have over 12 volts on both terminals of both breakers.

Note that when hooked to shore power and the converter running, you have about 13.8 volts. But when on battery only, you have typically about 12.5 volts. At 12.5 volts, the hydraulic motor pulls more current than it does at 13.8 volts. So the breaker is more likely to trip on battery only than on shore power.

I thought from pictures of the newer units with an inverter for the fridge, that power ran thru its own 12v breaker.
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Old 08-06-2018, 10:35 PM   #6
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On our rig, the breaker that feeds the hydraulic pump is the same one that feeds the 12 volts to the panel, so if yours is the same, when the breaker is open, not only will you not have power to the hydraulic pump but the batteries are not feeding the panel either. Once you connect shore power, the converter is powered and is energizing the 12 volt side of the panel, so that's why you have 12 volts once you are on shore power.
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Old 08-12-2018, 01:21 AM   #7
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So today I got my 80 amp breakers. They're basically the same ones Bob and Becky showed.

Much to my chagrin, the posts are larger and, of course, don't fit the ends of the cables as they are today.

I know that removing the ends and crimping correctly sized ones on is a possibility, but not one I love. These are much larger than the ones I've worked with in the past, so I don't have the right parts. I can get them, but there isn't a ton of spare cable on most of these connections, which means I'd have to gracefully remove the existing connectors and replace them. Lots of room for error there and I'm not overly electricity savvy.

Is there some kind of adapter I can use to make the smaller connectors work on the larger posts?

I honestly didn't even consider this until I had the first line in my hand. /sigh

Here's a pic. Advice appreciated.

Thanks,
Jeremy

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Old 08-12-2018, 07:35 AM   #8
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As you and I both know, the CORRECT way to fix is put larger terminals on end of the wires.

Since you already stated you're not comfortable doing that MAYBE another idea would be to drill the current holes to a larger diameter.

I don't know if there is an adapter that will screw onto the larger terminal to make it smaller or not.

Keep us posted on your solution and outcome of your original problem.
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Old 08-12-2018, 08:10 AM   #9
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I would just drill out the hole. Looks like there is adequate metal to do that without compromising its integrity.
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Old 08-12-2018, 09:34 AM   #10
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If you drill it out, use a Unibit instead of a regular drill bit. may have to approach it from both sides. Then if you drill it out check it for overheating with an IR thermometer. If the connection is getting hot, you will have no choice but to redo connector.
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Old 08-12-2018, 09:43 AM   #11
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I'll just add a 12V issue we had a couple of years ago. Were getting some weird 12V reading and finally traced it down to the Battery Disconnect Switch, the nuts on the terminals were so loose, one was ready to fall off. Once tightened no more 12V issues.
Just something else to look at.
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Old 08-12-2018, 09:46 AM   #12
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Bierp what size is that wire? I have some no. 4 crimps for my current project and I have a few extras. The stud size is 1/4". I have to go to the electic supply house tomorrow morning to get some additional lugs for larger studs. Let me know if the lug I have will help. We are very close geographically.


There is a lot of meat still left on that connector. I would just drill it out.
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Old 08-12-2018, 10:08 AM   #13
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Go ahead and drill it out. It won't hurt anything. Just make sure you hold the lug with a vice grip or pliers so that it wouldn't rip your hand when you drill.
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Old 08-12-2018, 10:21 AM   #14
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Quote:
Originally Posted by rohrmann View Post
Every time you operate the jacks, you are operating them with 12 volts, because they are directly connected to the batteries. The breaker that is wired between the batteries and the hydraulic pump is the one that should be replaced with an 80 amp breaker, either a manual reset or an auto reset. The photo shows a manual reset that I installed in our rig.
Where did you get this breaker? We have a 150amp of the same design for the converter and no one around here carries it (or even knew what it was for that matter)!
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Old 08-12-2018, 10:57 AM   #15
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I think this is it

https://www.amazon.com/dp/B008QDI9HY...v_ov_lig_dp_it
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Old 08-12-2018, 12:19 PM   #16
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Mine is actually this one: https://www.amazon.com/Tocas-Circuit...dp/B07B8BX3P2/ but basically the same thing.

I might look deeper to see if I can match the stud size. Drilling might work for the big gauge stuff, but if you notice my first post pic, there’s a lot of small gauge stuff I’ll need to manage too.

Fireguy, thanks for the offer. I’m actually at Glacier National Park for the next week or so and I’m hoping to knock this one out while I’m on the road. We’ll see about that, but for now I’m good. Thanks!
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Old 08-12-2018, 02:18 PM   #17
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When I changed out my breaker, I drilled out the ring connectors. On our rig, like I said, there are only the #4 cables to that breaker. The second breaker has a number of small wires, and that breaker has never failed. While I was doing the work, I did discover a couple of loose connections at the pump terminals, and fortunately there was no evidence of arcing, so I just tightened them.
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Old 08-12-2018, 04:43 PM   #18
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Oh if you don't have a drill handy (and everyone should who owns an RV) you can use a small round file (like a chain saw blade sharpener would use) to open the hole up. Or a rotozip or dremel.....dang I gotta go get some more tools LOL.......
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Old 08-15-2018, 02:48 PM   #19
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Ditto on enlarging the terminal holes. Very cautious in doing so because a bit will want to grab in the last bite. A reamer would be better.
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Old 08-15-2018, 03:01 PM   #20
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On my coach I have a separate 50 amp breaker that looks just like those 50s but it has a VERY SMALL button on the end of it - that pops out and you have no power going to the batteries. Look at all of your circuit breakers out there and see if you have one that popped. Mine is on a copper bus with other breakers as well but all are under where you are at.
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