Hi everyone,

    I posted about a month ago for some help with Troubleshooting my power converter.  The original post is here: http://www.horsetrailerworld.com/forum/thread-view.asp?threadid=19032

   In short, when unplugged my battery was not powering what it should.  Found out there was a blown fuse on the power converter, replaced the blown fuse and all was working great!  Well, this past weekend when at a show my lights and everything were not working off of my battery (they had been working great the past month or so since I replaced that fuse).  Got home and sure enough, that same fuse was blown again!  Replaced it, and everything went back to working normally.

    From what you all told me on here and from my researching, the only way that fuse should blow is if the battery is hooked up incorrectly?  However, the battery has not been messed with at all, still hooked up correctly.  What else could blow that fuse? 

  Thanks for your response!

   A lot of the info you have asked is all on that post I copied the link to, that is why I did not include it.  Sorry about that!  It is a WFCO converter (model:WF-8740 40 Amp Power Center), and I have read the manual (I am not the most electrical-savvy so I had my Dad read it as well).  The fuse that keeps blowing (battery protection fuse), from what I gather from the manual, can only be blown if a the battery is hooked up incorrectly.  I replaced it with the correct size fuses (15A), so I don't think that is it.. And also like I said it has been working just fine for the past month or so (hauled and used probably 5-6 times in that period).  It is a weekender, so as far as appliances all it has is a fridge, microwave, water pump (no water heater) and lights as well as outlets.  The only things that the battery actually powers when not hooked up to a plug in power source is the lights (inside the LQ and the lights in the horse area and outside of trailer) and water pump.

    I guess it is possible that I overloaded the circuit?  But I've used it many times and have had lights on while running the water pump no problem.  Not sure what else would have sent it over the edge?

A forty amp converter powers both DC and AC circuits. The DC circuits will usually have fuses for protection, the AC will have breakers. The capacities of each circuit will be dependent upon the wire gauge used. The B+ charging circuit is usually a 12 or 14 AWG wire, which would limit the fuse size to maximum of 15 or 20 amps. The converter's protective fuse isolates the converter from both reverse polarity and any shorts that would overload the unit.

If the wiring was installed with the polarity being incorrect, the unit would not have worked at all, instantly blowing the protection fuse as soon as power was applied. Because it has worked normally for a short time, I suspect you have an intermittent short in one of the circuits leading from the converter. The easiest way to determine if it is one of those circuits, is to pull the fuses or trip the breakers one at a time. The bad circuit can be identified, when the converter continues working normally, without the fuse being burnt.

It will then be a matter to determine what draws you have on that circuit. Most shorts occur at junctions, where wiring is combined, fixtures are installed or the wiring passes through an opening. It could be a bad switch, bulb base, or a wiring loom grounding on a bulkhead. Look for particular items that aren't working, or those that are intermittent. They would indicated the first circuit I would isolate for the trouble shooting.