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Author Topic: Positive to ground inline fuse popping  (Read 591 times)

Jaycoskippy

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Positive to ground inline fuse popping
« on: September 17, 2017, 11:27:17 PM »
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.
« Last Edit: September 18, 2017, 12:30:58 AM by Jaycoskippy »

HueyPilotVN

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Re: Positive to ground inline fuse popping
« Reply #1 on: September 17, 2017, 11:41:08 PM »
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.
Bill Waugh
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35 years on the road

Jaycoskippy

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Re: Positive to ground inline fuse popping
« Reply #2 on: September 17, 2017, 11:52:23 PM »
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

TonyDtorch

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Re: Positive to ground inline fuse popping
« Reply #3 on: September 17, 2017, 11:52:52 PM »
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  ... 

     
« Last Edit: September 18, 2017, 12:10:33 AM by TonyDtorch »

Arch Hoagland

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Re: Positive to ground inline fuse popping
« Reply #4 on: September 18, 2017, 12:10:00 AM »
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?
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Jaycoskippy

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Re: Positive to ground inline fuse popping
« Reply #5 on: September 18, 2017, 12:16:06 AM »
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

Rene T

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Re: Positive to ground inline fuse popping
« Reply #6 on: September 18, 2017, 07:33:52 AM »
Did you make any electrical changes just prior to this happening like maybe changing out the converter or did you change out the batteries?
Rene & Lucille & co-pilot Buddy
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Gary RV_Wizard

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Re: Positive to ground inline fuse popping
« Reply #7 on: September 18, 2017, 07:55:35 AM »
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.
Gary
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Summers: Black Mountain, NC
Home: Ocala National Forest, FL

skeeter_ca

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Re: Positive to ground inline fuse popping
« Reply #8 on: September 18, 2017, 09:28:56 AM »
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

Jaycoskippy

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Re: Positive to ground inline fuse popping
« Reply #9 on: September 18, 2017, 09:45:02 AM »
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.

TonyDtorch

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Re: Positive to ground inline fuse popping
« Reply #10 on: September 18, 2017, 01:39:46 PM »
Take a picture of it for us to see... :)

OBX

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Re: Positive to ground inline fuse popping
« Reply #11 on: September 18, 2017, 02:01:23 PM »
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?

Jaycoskippy

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Re: Positive to ground inline fuse popping
« Reply #12 on: September 18, 2017, 02:31:14 PM »
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.

grashley

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Re: Positive to ground inline fuse popping
« Reply #13 on: September 18, 2017, 06:42:58 PM »
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.
Preacher Gordon
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NY_Dutch

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Re: Positive to ground inline fuse popping
« Reply #14 on: September 18, 2017, 06:55:45 PM »
I expect the terminal strip with the fused wire from the battery positive terminal connected is actually insulated from the trailer ground.
Dutch
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meternerd

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Re: Positive to ground inline fuse popping
« Reply #15 on: September 20, 2017, 08:55:43 PM »
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.
« Last Edit: September 20, 2017, 09:20:41 PM by meternerd »

Lou Schneider

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Re: Positive to ground inline fuse popping
« Reply #16 on: September 20, 2017, 10:33:48 PM »
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.
« Last Edit: September 20, 2017, 10:36:22 PM by Lou Schneider »

skeeter_ca

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Re: Positive to ground inline fuse popping
« Reply #17 on: September 22, 2017, 05:56:09 PM »
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

TonyDtorch

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Re: Positive to ground inline fuse popping
« Reply #18 on: September 22, 2017, 07:09:20 PM »
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.
« Last Edit: September 22, 2017, 07:12:30 PM by TonyDtorch »

skeeter_ca

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Re: Positive to ground inline fuse popping
« Reply #19 on: September 22, 2017, 10:56:22 PM »
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

Ernie n Tara

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Re: Positive to ground inline fuse popping
« Reply #20 on: September 23, 2017, 07:14:18 AM »
You can get an arc regardless of which terminal is connected last; it's exactly the same connection? 8)

As far as currect flow goes, most tech's, including me, were taught the negative to positive flow theory. But, if you ask a physicist he will swear it's positive to negative. It makes no practical difference for our purposes.

And we're not going to get into solid state components where holes flow instead of electrons. :(

Ernie
Ernie 'n Tara

2011 Winn Journey 34y
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Gary RV_Wizard

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Re: Positive to ground inline fuse popping
« Reply #21 on: September 23, 2017, 09:43:04 AM »
Quote
Actually not trying to get to picky but electricity really flows from negative to positive.

LOL! Somebody was bound to bring that up, but it's irrelevant. The electrical potential (voltage) is considered to be from Positive to Negative, even though that's a design convention more than a physical fact about how the electrons actually move about.  Some DC electrical devices don't care which pole is which, but the ones that do are designed based on the convention that flow is from positive to negative. If you try to switch the polarity, those devices won't work (led lighting is a common example).

And then there is the solid state logic stuff that Ernie mentioned. Let's not go there...  :D

For those that would enjoy a relatively simple overview of DC current flow convention vs the actual physics, see https://www.allaboutcircuits.com/textbook/direct-current/chpt-1/conventional-versus-electron-flow/
 
« Last Edit: September 23, 2017, 09:46:44 AM by Gary RV_Wizard »
Gary
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Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Free Spirit

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Re: Positive to ground inline fuse popping
« Reply #22 on: October 08, 2017, 08:15:55 AM »
The fact of the matter is that electrons (electricity) flows from negative to Positive. Way back when, the founding fathers of electricity thought that electricity flowed from Positive to Negative. Later on, when it was discovered that electricity actually flowed from Negative to Positive the electrical geniuses at the time decided that for all intents and purposes, it didn't matter. It didn't matter because the formulas and practical applications were not affected in any way. Everything still worked just fine either way and so it was decided to stick with the existing convention rather than cause confusion. The physicists, mathematicians, electronics industries and all those otherwise involved in electricity understand this concept that electrons actually flow from neg to pos and so still stick to the original concept rather than change because it doesnt matter.
TonyB
Retired and full time living aboard our Denali 293RKS. We plan to start serious cruising around mid-Dec.of 2017
Don't know much about RV"s in general and are still learning. First lesson learned is that dealerships are not responsible for anything and warranties can be used for toilet paper

Free Spirit

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Re: Positive to ground inline fuse popping
« Reply #23 on: October 08, 2017, 08:20:19 AM »
Ome way to isolate the problem would be to remove all the DC fuses. The install the main neg. to ground fuse. Ig the fuse pops, then the problem is with the main power cables. If it doesnt pop the main fuse, add one fuse at a time. When you hit the fuse that pops, that is the component where the problem exists.
TonyB
Retired and full time living aboard our Denali 293RKS. We plan to start serious cruising around mid-Dec.of 2017
Don't know much about RV"s in general and are still learning. First lesson learned is that dealerships are not responsible for anything and warranties can be used for toilet paper

 

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