Univolt does not seem to be working

[Airboutique]

My lights and furnace fan only work when the breaker switch to the univolt is off. I have checked the fuses which all seem fine but I wonder if the big "40" fuse in the back of the univolt is bad would it cause the problem? This is my
first and probably last Winter in the mountains. I've been pretty resilent but the daily frozen pipes and lack of heat are wearing me out I would appreciate any ideas. Shelly

[SteveH]

Originally Posted by Airboutique

My lights and furnace fan only work when the breaker switch to the univolt is off. I have checked the fuses which all seem fine but I wonder if the big "40" fuse in the back of the univolt is bad would it cause the problem? This is my
first and probably last Winter in the mountains. I've been pretty resilent but the daily frozen pipes and lack of heat are wearing me out I would appreciate any ideas. Shelly

That seems backward from reasoning. Are you sure the breaker switch is not mislabled?

If you have a voltmeter of any type, it's a simple thing to measure the DC voltage with the univolt turned on, and off to verify it's working. And, if you have a battery in the trailer that is in good state of charge, the 12 volt appliances should work whether the univolt is working or not.

[dlb435]

Is the Univlot making the humming noise? Is it slightly warm?
I replaced my Univolt with a newer model conveter whan it failed. Not an easy job. You really do need a volt meter to check this thing out. Better yet would be a good electician.
You can pick up a nice digital volt meter at Home Depot or any place like that. You shouldn't have to spend more that $30.00 for one that will work for this job.
A fully charged 12 volt battery should read 13.85 volts.

[Wazbro]

Originally Posted by dlb435

A fully charged 12 volt battery should read 13.85 volts.

A fully charged battery should read about 12.85 volts and about 13.85 volts while the Univolt is charging it.

[Lumatic]

A voltmeter will tell you if the Univolt is putting out as above. All you need to test the fuse is a simple 12v test light.

I agree it does not seem to make sense that the furnace and lights only work with the breaker off. If this were the case all 12v systems would be working directly off the battery. If your battery is bad: it can run down really quick or if it is completly shot then you could only have 12v if you have 110 on running through the Univolt.

I also agree if you have problems with the Univolt besides fuses, Junk it.

If the 40 amp fuse is blown, any idea what could have caused it? Those puppies are hard to find. Univolts used 2 different sizes over the years. The big ones can sometimes be found at audio shops that have some older parts. For the smaller ones you can also put it a auto resetting fuse. But again, you should figure out what is causing the fuse to trip and fix it.

[dlb435]

Originally Posted by Wazbro

A fully charged battery should read about 12.85 volts and about 13.85 volts while the Univolt is charging it.

You are correct, I should have been more clear.

[Excella CM]

Shelly, first of all are you hooked to an exterior 110 volt source? If not, the Univolt is not functional since its purpose is to convert externally supplied household voltage into battery voltage to run the trailer and charge the batteries. If you are hooked to "shore power" (external 110V) you're probably correct in assuming a fault with the Univolt and then yes, check the fuse.

[Airboutique]

It was the 50 amp fuse. Thankfully found a replacement at NAPA auto parts. I am soooo happy to be warm and cozy. Now I need to start
searching for someone in the area to remodel my bathroom. Thanks
again everyone. I love this forum.

[Aage]

Gotta wonder why a big brawny fuse like that 50 amp one would blow, don't you?

I mean, when will it go again, on the coldest, stormiest night in the year at 3AM when all the stores are closed, or was it just a fluke that it let go in the fist place...?

Might be worth looking into, if you have the time and inclination!

[TG Twinkie]

If it was the original fuse it probably failed mechanically. If it wasn't melted in the view window it probably just became detached from one of the end caps. Vibration and corrosion would be the culprit.

[Wazbro]

I hope you got at least 2, maybe 4.

[Chatthayer]

my interior lights, etc. used to work on 12v without being connected to 110v. just the way they are suppose to......

now, when i disconnect the 110 there is no 12v making it to the lights, etc.. the battery is fine.

is this a univolt problem?

[Chatthayer]

also...is there a fuse box in my tradewind?

[TG Twinkie]

The fuse box should be part of or close to the Univolt. Some Univolts have the fuses mounted in one end, behind a door that opens.
How do you know the battery is fine?
One more thing to look for is a fuse on the common/ground side. It will be a large fuse, 30 - 50 amp. Mounted on the skin of the trailer. Not far from the Univolt. Trace the wires that go between the Univolt and the battery.

[Chatthayer]

Thanks to all the helpful Streamers....I discovered that my battery ground fuse was blown. Now all my strange symptoms of no 12v when unpluged; turning on and off lights making the radio go on and off, making me almost crazy are gone.