Positive to ground inline fuse popping

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Jaycoskippy

Member
Joined
Sep 18, 2017
Posts
5
Hello, I have a 94 jayco that developed a new problem that is causing me to rip my hair out.
    The 20 amp fuse that is inline coming off the positive terminal to ground blew out on us today. I have checked everything I can that I know of. Our 12v system is down, I checked dc across the battery, ground continuity, fuses, breakers all of it I can't find anything that would cause the fuses to arc the second they go back into the fuse holder.
Edit: 24v to 12v because I'm an idiot.
 
A connection from the positive lead of your battery to ground is a dead short and will certainly blow a fuse.

ground should connect to the negative post of your battery.
 
That's what I was thinking but we bought it while it was wired like that with no issues it just suddenly went out on us today
 
What do you have in your RV that is 24 volts ?  most RVs have a 12 volt system.

sounds kinda like you have the cables joining two 12 volt batteries incorrectly connected to me.

two battery- 12 volt connections should look like one of these  ... 

   
 

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There are special circumstances where a positive ground is used. I wonder if the previous owner wired this RV to have a positive ground.

If so you would have instant problems when you plugged into shore power if you weren't aware of the positive ground.

One of the things that makes me wonder is the use of 24 volts. That would indicate special wiring for something added to the RV.

We need more information.

How long have you had it?

Does it blow the fuse if not connected to shore power?

If you use a voltmeter and check the DC voltage from the positive battery lead to a chassis ground what voltage do you read?

If you measure from the negative battery terminal to a chassis ground what voltage do you read?
 
I misspoke earlier I have a single deep draw 12v marine battery from positive to ground I have 12v neg to ground is 0 from positive terminal to battery side fuse holder is 12v to trailer side is 0. I have had it for a few months, everything was working perfectly until today it popped at can't figure out where the short is
 
Did you make any electrical changes just prior to this happening like maybe changing out the converter or did you change out the batteries?
 
There are a few cases where a positive ground is used, but an RV isn't one of them. And a ground is not normally fused either, though there is nothing wrong with that. The battery ground would require much more than a 20A fuse, though.

Check to see if there is another wire from the battery negative to the chassis.  If so, that is your "ground" and the 20A wire is for something else. What is it connected to on the other end? It should NOT be the chassis or body of the RV.
 
I'm sure the positive does not go to ground. You must be mistaken. Can you follow the wire after it leaves the fuse and see exactly where it goes.

skeeter
 
Inside the battery compartment there is a row of screw studs booked to the metal frame 2 black wired come out of the body of the trailer and attach to it and the wire with the inline fuse go to it. The other wire from the positive goes back into the body.
 
If this just started I have to ask... did you take your battery out and reinstall it recently?  If so, did you look closely to make sure the battery is not turned around?
 
I've been troubleshooting all morning and I have narrowed it down to a bad or wonky converted. Took the battery out and got it tested hooked it back up with no converter and everything worked fine. Hooked the converter back to it and the fuse instantly blew.
 
You do have negative ground.  Voltage Neg to G was -0-.  Voltage Pos to G was 12V.

Power flows from the batt pos terminal to the fuse block or from the terminal strip thru a fuse, then to the load (Light, motor, circuit board, etc) then to ground.

It sounds like you have identified the source of the problem.  Post the model number on the converter and others can recommend a replacement.
 
Jaycoskippy said:
I misspoke earlier I have a single deep draw 12v marine battery from positive to ground I have 12v neg to ground is 0 from positive terminal to battery side fuse holder is 12v to trailer side is 0. I have had it for a few months, everything was working perfectly until today it popped at can't figure out where the short is

I'm confused....you said positive to battery side of fuse holder is 12V to ground.  You said to the trailer side is zero.  Is that with the fuse blown?  A fuse is just a wire, so how can you have a different reading from the line to load side?  I'm an electrician, so maybe my terminology is different, but...if you have a VOM, pull the fuse and measure load side resistance of the fuse holder to ground and also read it at the converter positive battery connection.  To avoid blowing fuses, measure the positive terminal of the converter to the negative terminal.  make sure your meter has the polarity correct.  If it reads near zero ohms, you may just have a wiring problem in the converter.  Pull all of the fuses and measure it again.  If it changed, put the fuses back in one at a time to see if any cause the reading to drop.  Basically, just try to narrow down what is causing the reading to be near zero.  May save you from buying a new converter.
 
A trick to keep from repeatedly popping fuses while tracing down a short is to replace the fuse with a 12 volt light bulb.  Put a pair of wires onto the bulb or use a lamp socket and connect them in place of the fuse.

While the short exists, the light bulb will glow at full brightress while limiting the short circuit current to a safe value.  When you eliminate the short the light bulb will either go out or glow at reduced brightness, depending on what else is on the circuit.
 
grashley said:
Power flows from the batt pos terminal to the fuse block or from the terminal strip thru a fuse, then to the load (Light, motor, circuit board, etc) then to ground

Actually not trying to get to picky but electricity really flows from negative to positive. That is why they always recommend removing the negative cable first to reduce arcing. Just FYI
Skeeter
 
The reason they say to remove the negative first is because the ground is negative,  and if the wrench comes in contact with any structure it won't explode.

on older American cars and British cars that are positive ground you are told to remove the positive lead first.
 
That is one reason, but with the use of a lot of sensitive electronics in cars these days arcing can cause damage which is one more reason to always remove the negative first and install it last.

skeeter
 
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