Forum Discussion

js6343js6343's avatar
js6343js6343
Explorer
May 15, 2015

Blown fuse help

I pulled my TT from storage the other day and hooked up a freshly charged battery. First the positive terminal then negative. I noticed quite a spark when I connected the negative terminal, but thought that should not be a that unusual. But I double checked the polarity as OK just to be sure.

I entered the TT and found that all my 12V endpoints do not work. Went to the fuse panel and found both main 40 amp fuses blown.

Anyone have any ideas what would cause both main fuses to blow. I will go ahead and replace them today, but am concerned I might have an underlying problem. Though I am not sure what that would be.
  • K_Charles's avatar
    K_Charles
    Explorer
    May 15, 2015
    If both polarity fuses blew you need to recheck the polarity. Don't go. Y the color of the wire, find the one that goes to ground and hook that one to the "-" post.
  • Dick_B's avatar
    Dick_B
    Explorer
    May 15, 2015
    Sounds like a short circuit that was open until you made the second connection. If the rig was grounded connecting the positive side of the battery would have blown the C/B also.
    Of course, where the short is...? Anything different from when you put the rig away? Any new work? If it was me I'd hustle the RV to my dealer who has smarter people working there than I.
  • RJsfishin's avatar
    RJsfishin
    Explorer
    May 15, 2015
    Those are not polarity fuses, but they mite have blown if polarity was backards.
    Otherwise look for a dead short circuit. Remove all other DC fuses, then check again. Use process of eliminization ! :)
  • westend's avatar
    westend
    Explorer
    May 15, 2015
    Do you have a wire that was on the battery that is now disconnected and laying on the frame? If that circuit was powered that may have caused a short circuit. To blow the 40 amp main fuses, you would need to have a dead short or reversed the polarity.
  • js6343js6343's avatar
    js6343js6343
    Explorer
    May 15, 2015
    A piece to the puzzle. I put a meter on the battery. This polarity is reversed.

    This can happen????? I did not think a battery could reverse polarity. How does that occur?

    Maybe a short in the battery. Is it possible that I charged the battery with reverse polarity? How would I fix that?
  • js6343js6343's avatar
    js6343js6343
    Explorer
    May 15, 2015
    Read a little on the internet. I must have charged it in reverse polarity. Or the kids fooled with it. (That will be my story.) The battery is probably toast.

    Duh.
  • azrving's avatar
    azrving
    Explorer
    May 15, 2015
    You may have mixed up the wires at the battery. As said above, find the one that goes to the frame of the trailer and connect it to negative. When you get iit figured out mark the wires. A nice up grade is a blue seas battery switch while in storage.
  • Chris_Bryant's avatar
    Chris_Bryant
    Explorer II
    May 15, 2015
    RJsfishin wrote:
    Those are not polarity fuses, but they mite have blown if polarity was backards.
    Otherwise look for a dead short circuit. Remove all other DC fuses, then check again. Use process of eliminization ! :)


    Actually, those are polarity fuses- they have no other purpose. They will not blow due to an overload, as they are above the output of the converter. Modern converters are self limiting on output current, and need no fuse protection.
  • js6343js6343's avatar
    js6343js6343
    Explorer
    May 15, 2015
    No. Did not mix up the wires. Negative post connected to the frame.

    Its the battery. I pulled it from the TT. Walked the battery into the garage. Put a meter on it. The posts are reversed in polarity.

    $100 down the drain.
  • js6343js6343's avatar
    js6343js6343
    Explorer
    May 15, 2015
    Glad there are polarity fuses for this purpose. Or I might have much bigger problems

About Technical Issues

Having RV issues? Connect with others who have been in your shoes.24,187 PostsLatest Activity: Jan 14, 2025