Mysterious busted fuse

[alanaks]

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?

[westend]

I'd suggest you get some "hands on" help. The information you're giving is not enough for a diagnosis over the Internet.

[alanaks]

bguy wrote:
So you're saying you put in a new (known to be good) fuse and it blew right away or the new fuse failed to energize the circuit?

The new fuse did nothing. 😕

[bguy]

So you're saying you put in a new (known to be good) fuse and it blew right away or the new fuse failed to energize the circuit?

[alanaks]

campigloo wrote:
Are you sure nothing else changed? If some of the 12v system works I don't think the problem would be at the battery. The heater should run on 120 a/c; nothing to do with fuses. 120 should have breakers as safety devices, not fuses. I drove myself crazy tracing 12v circuits until it finally dawned on me to check the light bulb I had recently replaced. It worked fine when I put a single pole bulb in the socket instead of the double pole I put in it.

Yeah, nothing else changed. I understand too, that the heater (running on AC) should not have affected the fuses...but honestly, everything was working before I left for work, and then the lights wouldn't turn on when I got back. Again, I found a blown fuse, replaced it, and nada. I'm sure it's the right fuse...

[alanaks]

opnspaces wrote:
There must be more than one fuse blown. Try taking another 10 amp known good fuse and use it to substitute the other fuses one at a time. It won't matter too much if it's the wrong size for the test. Just make sure you put the original fuse back in it's place after you're done.

Tried that. 😕

[alanaks]

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.

[campigloo]

Are you sure nothing else changed? If some of the 12v system works I don't think the problem would be at the battery. The heater should run on 120 a/c; nothing to do with fuses. 120 should have breakers as safety devices, not fuses. I drove myself crazy tracing 12v circuits until it finally dawned on me to check the light bulb I had recently replaced. It worked fine when I put a single pole bulb in the socket instead of the double pole I put in it.

[westend]

Typically, lights in an RV are powered by the 12V system. Powering a 120V device should have no effect on the 12V system unless the draw of the heater tripped a GFCI or a circuit breaker, that circuit protection also controlling the onboard converter.

As others have said, typically, there is a circuit breaker between the battery and the 12V distribution panel and the battery, usually located close to the battery. There may be a small button on the circuit breaker to reset it.

Good reading:12 volt side of life

[RoyB]

The 120VAC circuits use circuit breakers and the 12VDC circuits use DC fuses...

The 120VAC Electric heater would have tripped a 120VAC Circuit breaker or possibly tripped one of the GFCI push buttons. My trailer has these GFCIs at three locations in my trailer - Sink area, Bathroom sink area, and sink area next to bedroom... (i.e. anywhere yu can come in contact with water)

Roy Ken

[opnspaces]

There must be more than one fuse blown. Try taking another 10 amp known good fuse and use it to substitute the other fuses one at a time. It won't matter too much if it's the wrong size for the test. Just make sure you put the original fuse back in it's place after you're done.

[Beachums]

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?