Blown Fuse

Sounds like your main fuse and 15 amps is not enough. A 30-40 amp would be more appropriate. Could be it was the only fuse available at some point in time.

The fuse was fine until something caused the home GFI to trip when it was plugged into our home. That's when the fuse started blowing. I need to find the wire diagram to find out what it might go to and see what might be causing this. Like I said if I plug the trailer into the house that 15 amp fuse blows also.

Sounds like 12 volt ground leak.
How large is the wire that this fuse is on?

If you can see the AC to DC convertor easily there might be something grounding the output...say water dripping on it, corrosion or another reason for the high impedance ground leak.

That might be true about the leak. I tested the battery with volt meter and it was at 7 volts.
I will look at the wire tonight and let you know what color it is. can't see the converter very well with out taking it apart. I will try that also.

GFI's trip when the current drawn on the hot side is different than current drawn on the nuetral side indicating some current being drawn on the ground line. If your homes GFI is tripping then there is leakage somewhere to ground. It's not a dead short since a 30amp works. Be careful using too large of a fuse and melt wire or insulation instead!

Sounds like either a defective battery or convertor drawing too much current.

Just a thought but if the GFCI was tripped for any length of time and allowed the battery to run down its possible when you plug shore power or connect the 7 pin plug you are putting more than 15A of power into the battery due to its discharged state. Do you have a standalone battery charger you can use to top off the battery? A volt meter to check the approximate charge state of the battery?

Yes, this is a black wire that goes into the ceiling and I assume that it goes to the converter. I can't see inside the converter but I will remove it this weekend and see what I find.
The other day when this was happening I did measure the voltage of the battery and it was about 7.5 volts DC. So that might be the issue with drawing more amps because its low. I have had this battery for 2 years now but I didn't maintain it over the winter last year. I will remove the battery and have someone test it to see if there are issues with it. Then try to get a trickle charger and see if this happens again with a full charge on it.

The problem is that your converter can supply 30 or 40 amps of current to a dead battery which is enough to blow the fuse you have installed. A fuse doesn't care which way the current is moving it will blow anytime the current rating is exceeded. I would suggest using a good battery charger to see if you can charge the battery. At the voltage you stated it is really dead.

Yes, this is a black wire that goes to the top of the camper. The fuse is crimped on and is blue.
I think that my radio/dvd/cd player is what is running down my battery because there is no off switch on it.