No 12v power unless battery hooked up

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snyper2384

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Joined
Oct 29, 2012
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4
The electrical power system was fine till this morning . woke up and none of the 12 v lights worked and the house was cold as could be . didnt have the battery hooked up since i was on shore power . . but when i hook the battery up i have my 12v system till the battery died .
I bought the trailer used about 2 months ago.  its a 1994  34' wilderness with slide out  .  any help would be appreciated .
 

Alfa38User

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Oct 4, 2007
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6,676
Sounds like the converter has failed. Many converters (your battery charger and 12V supplier) do NOT like to run without the batteries in place, the batteries act like a filter and a steady load. The 120V circuit breaker to the converter may have popped. Did the furnace try and  run overnight??, (It draws quite a bit of 12V current for the fan and  a single battery will not last long when the furnace is operating if it is not on a constant charge!!! I have two and one cold overnight is about all it takes to discharge the pair using a 40K BTU furnace and when the 120V power has failed.

Many converters use fuses on the 12V output to act as a polarity protection in case the battery gets hooked up backwards. You may have blown one or both but ..... 

Your next question will likely be "where is the converter?" Good question!!! It could be buried almost anywhere; One popular spot is directly behind the combined 120V circuit breaker and 12V fuse panel (if you have one) and is often part and parcel of it!!. In many cases the make and model of this combination is often marked on the cover or on the panel itself. Make a note of it for any future questions you may have.
 

John From Detroit

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Apr 12, 2005
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Davison Michigan
That said.. When a furnace first starts there is a rather large inrush of current.

IF you have a small converter, it may have simply popped it's fuse.

So before you "Throw money at it" check the fuse.
 

snyper2384

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Oct 29, 2012
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4
Ok i have checked the breakers and the fuses at the panels . but all the wires lead backards and into the floor . i am guessing its in the floor? all thats on the breaker box is the well breakers and a circuit board with 9 fuses all for lights and accessories . the converter is not part of the unit .  but under the front of the trailer there is a panel screwed on by about 16 #2 square head screws on the underside about 1foot by 1 foot that all the wiring from the battery goes to could that be where the converter is located at?
 

Alfa38User

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Oct 4, 2007
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Is there a manufacturers label on that circuit breaker/fuse panel or its cover?? Converters on some models of those panels are  fastened and wired on the back of those combined fuse/breaker panels.

Wouldn't hurt to look behind that panel you described but don't forget to seal it back up afterwards.
 

Alfa38User

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Oct 4, 2007
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6,676
Magnetek's usually have the converter behind and attached to the fuse/breaker panel. Unplug everything  and disconnect the battery and then remove the panel and you should see it. (There should be enough slack in the wiring to permit this...)
 

Gary RV_Wizard

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Feb 2, 2005
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Location
At our Silver Springs FL home
What was the Magnetek model number?  With that, we can tell if it contains the converter/charger or not.  Although, I suppose it is possible that a previous owner already bypassed an integrated charger and added an external one somewhere else, e.g. below the floor somewhere.  Is there a box wired to the batteries and near to them?
 

mwells4654

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Joined
Aug 8, 2012
Posts
6
Location
Oklahoma
The PO of my trailer installed a battery maintainer, I thought to keep the battery charged at home instead of plugging in the 30A trailer cable.  But that was not the case as we found out.  When we first took the trailer out for a weekend trip, we left a 12v. light on in the bathroom as a night light.  The 120v was plugged in so we thought the battery was being charged.  Next morning - no lights at all.  The rest of the trip I plugged in the battery maintainer and everything was fine.  After returning back home I checked the fuse panel and all of the fuses were ok - I removed the converter,  took it apart and found the main fuse inside the converter was blown.  Replaced the fuse, plugged in the converter and low and behold - it started humming (never did that before).  Everything works fine now.    It cost $1.43 for five fuses.  Oh, and I put in a 120v night light in the bathroom.  lol
 
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