Mysterious busted fuse

Beachums wrote:

alanaks wrote:
My travel trailer has lights powered by a battery that is currently hooked up to a trickle charger; the charger indicates the battery is fully functional. I have an extension cord with an external power source that I use to charge anything else.
A month or so ago, I left the space heater in my trailer on (low) for about 7 hours, which I'm pretty sure I'd done before, and I returned to find the lights inoperable. I looked at the fuse "box", and found one had blown.
I don't know which fuse is supposed to charge what; I unfortunately lost the handwritten list made by the previous owners who installed the lights, but I assumed since there was only one blown fuse it must be the culprit.
I bought a new one (10A) and installed it, but to no avail. Don't know what else could be the problem. :/ Any suggestions?

Without knowing what type of space heater you were using and how it was being powered, the most anyone will be able to give you is a guess. I see that you are saying that you are using an extension cord. Does that mean that it is powered by your house? I am assuming yes, but that is not 100% clear at this point.

Many travel trailers have an in-line circuit breaker between the battery and the converter. Most of the time they are external and corrosion over time is common. Are all of the other functions in the trailer working?

Yes, the space heater is powered by my house. I believe that what used to be considered the circuit breaker stopped working a year ago due to old age (it was VERY old) and instead of buying a new one, I simply replaced all of its functions with the extension cord.