Blowing fuses and receptacle question..

[Bluebamboo]

Hello All,

Our 86' 17ft BF blows the 15amp fuse under the left hand bench seat every time we plug into the tow vehicle? All seems fine once the fuse is replaced and not plugged into the TV but as soon as we 'hook up' it blows? Any ideas as to why this is happening or avenues to explore?

Also, possibly a bit of a silly question but do the plug in receptacles only work when connected to shore power?

Thanks for any thoughts.

Michael

[Des Nolan]

Hi Michael,

We had a similar, frustrating problem that took a professional auto technician more than one attempt to fix. I still don't understand exactly what was wrong but It had something to do with being grounded to the wrong spot -- back to the frame?

Look also at your tow vehicle wiring harness specs. Some foreign companies (Toyota in our case) fix it so that you have to use their product.

This may not help but it will at least give you a direction to look.

Des

[Thomas G.]

Originally Posted by Bluebamboo

Hello All,

Our 86' 17ft BF blows the 15amp fuse under the left hand bench seat every time we plug into the tow vehicle? All seems fine once the fuse is replaced and not plugged into the TV but as soon as we 'hook up' it blows? Any ideas as to why this is happening or avenues to explore?

What doesn't work when this fuse blows? How did you know to look at this fuse? You have a short somewhere, but you need to define which circuit to make it easier to find.

Also, possibly a bit of a silly question but do the plug in receptacles only work when connected to shore power?

Thanks for any thoughts.

Michael

The 110 volt outlets only work when plugged into the camp power, unless you have an inverter, which is unlikely.

[Carol H]

Micheal there can be many reasons for it. You could have a ground issue on the trailer side or the trailer/tow vehicles plug wires are corroded causing a short. I was also told once that if the trailers battery is very dead & you plug into the tow vehicle it may also cause the fuse to blow. Have no idea if the later is true or not.

Is this a new hitch wiring install on the vehicle or is the trailer new to you? If either is new then there is a good chance that the vehicle is not wired to match the trailers wiring. Also many of the newer cars have a little controller box between the 7 pin plug in point and where the wiring harness connects to the vechiles factory wiring. Often buried inside the vehicle's rear area. If that little box is malfunction it will give you all sorts of strange problems.

[steve dunham]

If you look at the fuse is it blown from an overload or a short circuit . (overload causes link to melt -- Short circuit cause link to melt but at a rapid rate usually with metal being splattered inside the fuse. When trouble shooting the fuse is often a good indicator of the source of the problem. I would check the connections to the TV and make sure they are connected properly . If the hot 12 VDC+ and Neg are crossed you would have a short circuit

[Steve L.]

My first thought was I wonder what changed, the assumption being that the O.P. had plugged in in the past without incident. If the trailer is new to him then the possibilities are almost endless.

I wasn't sure if it was a 12v fuse that was blowing, not being familiar with Scamps and the fuse locations.

I also wasn't clear if the receptacles he was asking about were 12v or 120v. 12v receptacles usually work plugged into shore power or not. 120v don't normally work without an inverter as pointed out.

[steve dunham]

It's possible you have a short or ground in the charging conductor coming from the tow vehicle . The fuse in the tow vehicle is blown and when you plug in the trailer you are back feeding this conductor from the trailer and blowing the trailer fuse . I would check to see if you have 12 VDC + at the tow vehicle plug . If power is present that would eliminate that as a source of the problem. (Some tow vehicles have an isolation relay so you may have to start the vehicle to make the test)

[Carol H]

Originally Posted by Steve L.

I wasn't sure if it was a 12v fuse that was blowing, not being familiar with Scamps and the fuse locations.

Steve the Scamps have two inline fuses one right at the battery and one just inside the house BUT the OP actually has a Bigfoot so not really relevant.

[Bluebamboo]

Hi @Des, @Tom, @Carol, @Steve D & @Steve L

Thanks so much for the suggestions...I will check them all out. We had the harness specifically installed for the BF, so I'm thinking this would not be the issue. Also, the fuse did not blow for the first couple trips so I'm thinking, as suggested, it may be a ground issue.

Alternately, I wonder if I've hooked the battery up incorrectly after charging and reinstalling. The BF has one white wire connection and one black wire connection...my thought was that black was always negative but perhaps the white is negative. Could incorrectly hooking up the battery cause this? Again, thanks all

Michael

[Thomas G.]

Originally Posted by Bluebamboo

........Could incorrectly hooking up the battery cause this? ......Michael

YES!

[Bluebamboo]

...oh, forgot to answer Tom. I found out about this fuse by posting here and was kindly answered with suggestions of checking under the seat for the fuse-an inline type.

[Bluebamboo]

Originally Posted by Thomas G.

YES!

Perhaps this is it then. Thanks!

[Carol H]

Originally Posted by Bluebamboo

..my thought was that black was always negative but perhaps the white is negative. Could incorrectly hooking up the battery cause this? Again, thanks all

Michael

Yup it sure can! Another member had a great deal of costly damage done to their trailers electrical system recently when the battery on their trailer was installed incorrectly.

+ Positive to Black & - Negative to White. Which is not the same as a car.

[Bluebamboo]

...thanks Carol

[steve dunham]

Get a roll of 3M #35 marking tape RED and 3m #33+ BLACK and mark the positive and negative conductors . It will end a lot of the confusion and possibly save some of your equipment . I did this to my Scamp not just for me but for the next owner as well

[Thomas G.]

Originally Posted by steve dunham

Get a roll of 3M #35 marking tape RED and 3m #33+ BLACK and mark the positive and negative conductors . It will end a lot of the confusion and possibly save some of your equipment . I did this to my Scamp not just for me but for the next owner as well

Right. The color coding in the RV world is nutz.

[Bluebamboo]

Originally Posted by steve dunham

Get a roll of 3M #35 marking tape RED and 3m #33+ BLACK and mark the positive and negative conductors . It will end a lot of the confusion and possibly save some of your equipment . I did this to my Scamp not just for me but for the next owner as well

Good idea. Thanks.

[Francesca Knowles]

Originally Posted by Bluebamboo

Hi @Des, @Tom, @Carol, @Steve D & @Steve L

Thanks so much for the suggestions...I will check them all out. We had the harness specifically installed for the BF, so I'm thinking this would not be the issue. Also, the fuse did not blow for the first couple trips so I'm thinking, as suggested, it may be a ground issue.

Alternately, I wonder if I've hooked the battery up incorrectly after charging and reinstalling. The BF has one white wire connection and one black wire connection...my thought was that black was always negative but perhaps the white is negative. Could incorrectly hooking up the battery cause this? Again, thanks all

Michael

Jackpot... backwards connection= blown fuse. White as ground is universal in the RV world.

Lucky thing you've got that fuse, or who knows what you might have damaged inside the trailer...

Francesca

[Brian B-P]

Originally Posted by Francesca Knowles

White as ground is universal in the RV world.

Yes, white is nearly universally negative. Just as close to universal is a lack of labelling and documentation of wiring; close behind that is the refusal of people working on them to look at whatever documentation exists. All of this leads to assumptions, which are bad. If you don't know what a wire is for, based on reliable documentation of the specific trailer or physically following it to see what it connects to, I suggest not guessing.

I shouldn't be surprised by the reverse battery hookup since I got partway through doing this myself, but in hindsight it really doesn't make sense. Sure, we may expect black to be negative, but the other wire is white - not red - so shouldn't we realize that what we expect is clearly not what is happening, so we should do some investigation?

[Raz]

For what it's worth, when the trailer battery connection is reversed, the two battery voltages now add and the resultant current is limited only by the wire resistance of the charge line. No delay on those fuses opening. Raz