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Old 11-22-2020, 01:04 PM   #1
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12VDC power question - no battery power to trailer

Hello. Did not use our trailer for 3 years. Installed a new battery in 2008 Sabre 28RBFWS trailer, but slide/lights/etc. will not run unless connected to 120VAC or truck is running, feeding 12VDC through harness. Found the 12VDC self-reset circuit breaker near battery extremely corroded & no power coming across it, so replaced with a new one. It is wired with a heavy black battery wire to "BAT" terminal of breaker, and "AUX" terminal has three other wires off it. A heavy black wire I'm guessing is main 12VDC feed from battery to convertor/fuse panel, smaller black wire which appears to be 12VDC from 7-way plug, and a smaller red w/white stripe wire which I'm guessing is the 12VDC charge from the convertor? Before reconnecting wires, thought I should check so put a meter to them and I'm getting almost no resistance to ground on the heavy black wire on the trailer side of the breaker. Does not seem that any of these should be connected to ground. Any suggestions? Reluctant to re-connect power until I find out if this is supposed to be this way. Anyone have a wiring diagram or can point me to one? I understand they can be as rare as hen's teeth. Thanks!
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Old 11-22-2020, 01:17 PM   #2
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If the 12V items work when connected to 120VAC ( converter powering them) and when connected to the TV ( truck powering them) then is it most likely the battery. if the battery has been sitting for years then it is most likely dead. I suggest testing the battery without 120VAC or the TV connected. if the battery is dead, you can try removing it and connecting to a automotive type charger, but it may be too late. Do not try to charge with the converter as it may not work if the battery is totally dead.
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Old 11-22-2020, 01:23 PM   #3
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On your DC distribution panel there should be a high (30-50) amp main fuse, sometimes called the reverse polarity fuse. Pull that fuse and then check your resistance values again.
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Old 11-22-2020, 01:28 PM   #4
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Originally Posted by clitesm View Post
Hello. Did not use our trailer for 3 years. Installed a new battery in 2008 Sabre 28RBFWS trailer, but slide/lights/etc. will not run unless connected to 120VAC or truck is running, feeding 12VDC through harness. Found the 12VDC self-reset circuit breaker near battery extremely corroded & no power coming across it, so replaced with a new one. It is wired with a heavy black battery wire to "BAT" terminal of breaker, and "AUX" terminal has three other wires off it. A heavy black wire I'm guessing is main 12VDC feed from battery to convertor/fuse panel, smaller black wire which appears to be 12VDC from 7-way plug, and a smaller red w/white stripe wire which I'm guessing is the 12VDC charge from the convertor? Before reconnecting wires, thought I should check so put a meter to them and I'm getting almost no resistance to ground on the heavy black wire on the trailer side of the breaker. Does not seem that any of these should be connected to ground. Any suggestions? Reluctant to re-connect power until I find out if this is supposed to be this way. Anyone have a wiring diagram or can point me to one? I understand they can be as rare as hen's teeth. Thanks!
It's possible that something connected to the wire you mentioned is turned on and trying to draw current. Since "ground" is the return for whatever that item is you will show little or no resistance. Best to make sure EVERYTHING is turned off although you will probably still have the LPG leak detector in the circuit. About the only way to check to see that nothing is shorting this wire, disconnect it at the Converter/Power distribution center and then check resistance. It should now read infinite resistance.

A note:

Generally the wire from battery to circuit breaker, and on to the converter/charger is not "small" but rather a #8 gauge wire or larger.
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Old 11-22-2020, 02:44 PM   #5
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The Red with White tracer wire likely powers your slideout, jack or some other device directly without going through the 12-volt power center since the converter charge circuit uses the same heavy wire as the one that supplies the converter power from the battery. With both your converter and vehicle-supplied power working, only the battery and its wiring remain prime suspects since the vehicle power is going through the reverse polarity fuses in the converter and powering the trailer’s 12-volt circuits.

Check the battery voltage across its terminals with the vehicle and 120 VAC power sources both disconnected. If the battery isn’t dead, then that battery voltage should also be on the BAT terminal of the 12-volt self-resetting circuit breaker when measured to ground. Also, check your battery ground to the trailer’s frame and make sure there is a good clean and solid connection there.

A dead battery or bad battery ground connection are the most likely problem. A bad battery might give you a reading on your voltmeter but drop off under load so don't let a bad battery mislead you. After that, bad or miswiring from the battery to the 12-volt self-resetting circuit breaker or the circuit breaker itself is bad.
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Old 11-22-2020, 02:51 PM   #6
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OP stated in the first post, that they installed a new battery. Still should test it with a voltmeter.
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Old 11-22-2020, 04:13 PM   #7
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two small things...

Is the polarity at the battery wires hooked up correctly?

Did you look under the trailer ( follow the wires from the battery) and find usually a 4x4 electrical box with a small 1 inch fuse that may need to be reset by pushing tiny button on the side of the fuse...

see pic below
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Old 11-22-2020, 04:59 PM   #8
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All, THANKS for the pointers - will check if anything is turned on & disconnect battery cable at convertor, then will get back under there once it stops raining & warms up a bit. Will plan to get some photos.

A little more info: Did not use trailer for 3 years, "old" battery kept in our home during that time, but was already 7 years old so when it would not power slideout, I just assumed "bad battery" & picked up a new one. Connected to 120VAC in the driveway while packing/prepping & everything worked fine. On the road, stopped for lunch & "new" battery would not operate any of the 12VDC - slide, lights, pump, etc. - had to turn on tow vehicle. Exchanged battery (did not try it as was still connected to 120VAC), spent week at the shore & had same problem on way back home. Read some posts here pointing to the 30A 12VDC auto-reset circuit breaker near the battery (mounted on A-frame & exposed to the elements/road spray) but could not get any voltage on the AUX side, so replaced it with a new one. Old one & its connections were extremely corroded & broke the old CB getting it disconnected - also corroded inside. Had to use visegrip pliers on the internal metal parts of the terminals & bend back & forth until terminal broke, freeing the ring terminals. Cleaned everything up god with wire brush in a Dremel & put silicone grease on everything when I put it back together - hope that slows corrosion. Fingers crossed that it is just something turned on/returning to ground, as everything (except running off battery) worked fine before I disconnected CB. Thanks again all!
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Old 11-22-2020, 09:28 PM   #9
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Do you have a battery disconnect somewhere
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Old 11-22-2020, 10:29 PM   #10
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Quote:
Originally Posted by Flybob View Post
If the 12V items work when connected to 120VAC ( converter powering them) and when connected to the TV ( truck powering them) then is it most likely the battery. if the battery has been sitting for years then it is most likely dead. I suggest testing the battery without 120VAC or the TV connected. if the battery is dead, you can try removing it and connecting to a automotive type charger, but it may be too late. Do not try to charge with the converter as it may not work if the battery is totally dead.
If it is totally dead (discharged) an automotive charger will not charge it either unless it is a manual type charger. A dead battery is a throw away, a discharged battery may be able to be recharged.
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Old 11-24-2020, 09:07 PM   #11
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All, checked if anything was turned on per Titan Mike's advice & found nothing. Disconnected battery wire from convertor/fuse panel & what I took as a short went away, so must have been the propane leak detector as Mike said. Ground connections at A-frame were also corroded, so unbolted, cleaned up with Dremel/wire brush & re-connected with new hardware & silicone grease to hopefully resist corrosion. Feeling much better about things, re-connected everything to the new 30A battery circuit breaker and cautiously hooked up the new battery. All 12VDC now works slide, lights, pump! Plugged 120VAC back in and everything is back to normal and will operate on battery only, 120V only, or both. Thanks all for the info - really appreciate it!
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