30amp fuse between battery and junction box

[Kidd280]

Okay so we picked up unit and when we went to hook up with no help from the dealer we could not get the tongue jack to work.

Well waiting for the salesman to get service I attached the shore power and the jack worked great.

The service tech made it about 15 minutes after I was totally hooked up and shore power disconnected again.

He checked that fuse-it was blown, he replaced it showed me jack functioning and off we went.

Got 7 hours home and had shore power hooked up to sleep the night while still hooked to truck. Next morning got all disconnected and stuff easy.

Fast forward 2 weeks time to move break everything down including disconnecting shore power. Go to raise tongue to hook up and nothing. Check fuse blown again.

Reconnected shore power got it done and went on.

That fuse must be the main cause without it and no shore power I have nothing (lights, jack, furnace, etc). With no shore power and that fuse in lights are not bright so I feel battery isn't charging with the fuse out and with no shore power and fuse in the jack cannot lift camper.

Jayco says bring to dealer but they want me to drop it off and say it will be 2-3 weeks to get it even looked at. All dealers within 100 miles state the same or worse no new appointments till February 1.

Any ideas of cause, solution, or where to start investigating? I am assuming some type of short?

[shadester]

I'd start with the checking the batt condition. Looking for loose connections and such. Also check the fuse and make sure it's the proper amperage. It sounds like it has to be a pretty good short but apparently it isn't happening constantly. I'd replace the fuse and try to find what function is actually blowing it. It sounds like it may be a process but you need to start somewhere.

[Sundancer330]

Also make sure to use a 30amp slo-blow fuse, a standard fuse will sometimes blow under the startup load of the jack.

[RAurand]

Also, I have seen running the jack up to the stop will blow the fuse also.

[Kidd280]

Originally Posted by Sundancer330

Also make sure to use a 30amp slo-blow fuse, a standard fuse will sometimes blow under the startup load of the jack.

I will look into the slo-blow fuse.
But to clarify the fuse is blown before ever touching the jack. I was wondering if somehow shore power(converted to 12v) and battery power were "bucking".

[RoyBraddy]

Normally this fuse is there to protect your battery cables from overheating and starting a fire. Mine is inline with the converter/charger and my jack is wired into the battery ahead of it (directly to the battery terminal...)

If your fuse value should be larger than the rated DC output from the converter/charger unit... If you have a 55AMP Charger unit the fuse may blow when charging your battery if it draws more than the 30AMPS...

Not knowing what you exactly have I am just guessing at some of this...

The newer trailer sometimes have an auto reset circuit breaker in place of the in-line cable fuse. Then when it trips it will reset i self in a few minutes...

Your battery bucking comment is not an valid issue. One of the purposes of the on-board converter/charger unit is to charge your battery when you are on shore power..

Another item to check is the fluid level in your battery. If your on-board converter/charger is a non smart mode unit the styeady 13.6VDC output is known to boil out the battery fluids if on shore power for long time periods. If the fluid boils out then the battery may be harmed and have a shorted cell which may demand alot of DC current from the converter/charger blowing your fuse... Your battery terminals should read 12.6-7VDC when fully charged and this should jump up to 13.6VDC when on shore power. If the battery is real warm to touch and shows fluids around the caps then it may be harmed already.

Roy Ken

[Kidd280]

Originally Posted by roybraddy

normally this fuse is there to protect your battery cables from overheating and starting a fire. Mine is inline with the converter/charger and my jack is wired into the battery ahead of it (directly to the battery terminal...)

if your fuse value should be larger than the rated dc output from the converter/charger unit... If you have a 55amp charger unit the fuse may blow when charging your battery if it draws more than the 30amps...

Not knowing what you exactly have i am just guessing at some of this...

The newer trailer sometimes have an auto reset circuit breaker in place of the in-line cable fuse. Then when it trips it will reset i self in a few minutes...

Your battery bucking comment is not an valid issue. One of the purposes of the on-board converter/charger unit is to charge your battery when you are on shore power..

Roy ken

2017 reks

[RoyBraddy]

Your 2017 model should have smart mode charger etc... I thinking the battery is harmed... Measure across its terminals with a VOM meter. It should read 12.6-7VDC if fully charged. If a cell is shorted it will less than 10VDC or so... It will also get very warm to hot when on shore power before blowing the fuse.

If you just have one battery it will normally demand 17-20AMPS DC current when being charged from shore power if it has been reduced to its 50% charge state (around 12.0VDC before charging)...

If you add more batteries later on you will want to increase the value of the FUSE based on the 17-20AMP DC Current demand for each battery in the bank.

Since this is all new I would check that the Battery terminals are wired correctly. Look on the battery case and find the stamped word NEG (-) terminal and make sure this is the one that goes directly to frame ground near the battery. Probably uses a BLACK cable for hot +12VDC and WHITE cable for frame ground (-12VDC). This is different from the Auto Industry where they use RED for hot +12VDC and BLACK for frame ground (-12VDC).

I would definitely check the fluid levels of the battery as well - should be just above the cores inside. When one of my batteries failed it was the first cell closest to the +12VDC terminal that got boiled out. This battery would never get higher than 5-6VDC and had to be replaced.

Waiting two or three weeks with it back at the dealership would suck for me haha...

Roy Ken

[Kidd280]

Originally Posted by Sundancer330

Also make sure to use a 30amp slo-blow fuse, a standard fuse will sometimes blow under the startup load of the jack.

Can anyone suugest where to find one of these fuses?

We found a littelfuse 30amp but it is larger then a standard blade fuse.

Thanks.

[Sundancer330]

Originally Posted by Kidd280

Can anyone suugest where to find one of these fuses?

We found a littelfuse 30amp but it is larger then a standard blade fuse.

Thanks.

I didn't have any luck as others did locating 30amp slo-blow fuses at any of my local big box auto part stores or the RV dealer. I ordered mine along with enough fuses to replace anything in my RV fuse panel plus a few extra for the truck lights after a wire got pinched and blew the trailer lights circuit. I ordered from Delcity.net, purchased about 20 fuses and shipping for about $12

[TaftCoach]

I found them at Walmart but I'm a different area than the smaller fuses.

[Mikey]

Originally Posted by RAurand

Also, I have seen running the jack up to the stop will blow the fuse also.

X2. You may have one of the problems others have identified, but I'm betting RAurand is correct. I had the identical problem a year ago with a new rig. I quickly learned that over-retracting the jack can routinely blow this fuse.

When the jack reaches maximum retraction and you're still holding the retract button, the strain on the electric engine blows the fuse. That's why you don't find the blown fuse until you try to extend the jack next time - it blew at the very end of the last retraction (leaving you unaware that it blew).

There's a ring around the base of your jack leg to identify the maximum retract point. Watch it carefully as you retract the jack, and stay north of the line. Since I've been doing this, zero issues with the fuse, a standard 30 amp.

I always check the fuse before I roll out - it's easier to do if you get one of the fuses that illuminates when blown (easy to find online or at your local auto parts store). You need this fuse to be working when you tow. First, it allows your TV to provide a maintenance charge to your batteries. Second and more importantly, your electric brakes won't operate if the trailer breaks away without battery power.

I keep a bunch of these fuses in my TV glove box, but since I've been mindful of how far I run up the jack, I haven't needed one. Hope the problem is as simple as this for you as well.

[oldmanAZ]

Exactly what Mikey said. I've got a bunch of those fuses I haven't needed.

I'll add two things: You CAN'T wait and let off the switch when you hear the motor bog down (at least I can't). It's too late at that point - the fuse blows when the motor bogs.

Put a cover over the head of the jack to keep water out. If you live in an area where it rains and then freezes, you can end up with ice in the hitch head stalling the motor and blowing the fuse.

[Camper_bob]

Originally Posted by Mikey

X2. You may have one of the problems others have identified, but I'm betting RAurand is correct. I had the identical problem a year ago with a new rig. I quickly learned that over-retracting the jack can routinely blow this fuse.

When the jack reaches maximum retraction and you're still holding the retract button, the strain on the electric engine blows the fuse. That's why you don't find the blown fuse until you try to extend the jack next time - it blew at the very end of the last retraction (leaving you unaware that it blew).

There's a ring around the base of your jack leg to identify the maximum retract point. Watch it carefully as you retract the jack, and stay north of the line. Since I've been doing this, zero issues with the fuse, a standard 30 amp.

I always check the fuse before I roll out - it's easier to do if you get one of the fuses that illuminates when blown (easy to find online or at your local auto parts store). You need this fuse to be working when you tow. First, it allows your TV to provide a maintenance charge to your batteries. Second and more importantly, your electric brakes won't operate if the trailer breaks away without battery power.

I keep a bunch of these fuses in my TV glove box, but since I've been mindful of how far I run up the jack, I haven't needed one. Hope the problem is as simple as this for you as well.

Originally Posted by oldmanAZ

Exactly what Mikey said. I've got a bunch of those fuses I haven't needed.

I'll add two things: You CAN'T wait and let off the switch when you hear the motor bog down (at least I can't). It's too late at that point - the fuse blows when the motor bogs.

Put a cover over the head of the jack to keep water out. If you live in an area where it rains and then freezes, you can end up with ice in the hitch head stalling the motor and blowing the fuse.

+1 to both of these.

I blew that fuse once. Now I carry a whole assortment of fuses for the trailer and the truck.

But since I replaced/upgraded my jack, I don't have a fuse on the tongue of the trailer at all any more. I have a manual reset circuit breaker for the new jack, and the main power (near the junction box up front) has an auto-reset circuit breaker from the factory.

[bankr63]

Originally Posted by Mikey

Second and more importantly, your electric brakes won't operate if the trailer breaks away without battery power.

In both of my trailers, and others I have helped with this is not true. The breakaway switch is connected to the positive battery terminal with a separate wire that is not fused. (Not saying this is necessarily the case on all TT's though.) In this case, your brakes will work with a pulled breakaway as long as the battery has juice.

Also agree with PP's here. One of the most common reasons we see here for a blown main fuse is jack extension.

Third comment; I would not be replacing all my fuses with slo-blo. They make sense where you have devices with large starting surge loads like A/C or fridge, but on a standard circuit like the 12v outlet, you want the breaker to trip ASAP when shorted by, say, a kid sticking something like a finger or toy into the socket.

[Mikey]

Originally Posted by bankr63

In both of my trailers, and others I have helped with this is not true. The breakaway switch is connected to the positive battery terminal with a separate wire that is not fused. (Not saying this is necessarily the case on all TT's though.) In this case, your brakes will work with a pulled breakaway as long as the battery has juice.

Now I've got to check my rig to see if that's the case for me as well. Thanks for the info. It'd be nice to have a direct wire to the breakaway.

[Jags4Me]

Had this same problem on my 2016 Whitehawk. Went thru lots of 30amp fuses before finally found an article about the battery possibly being hooked up backwards. Campers are set up different than cars, so the negative is White , black is positive. Just check to make sure they didn't hook it up backwards from factory.

[Jags4Me]

Had this same problem on my 2016 Whitehawk. Went thru lots of 30amp fuses before finally found an article about the battery possibly being hooked up backwards. Campers are set up different than cars, so the negative is White , black is positive. Just check to make sure they didn't hook it up backwards from factory.

[Turbofan]

I found them on Amazon.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Mine blow often.
Also found 35amp self resetting circuit breaker from another vendor but haven't installed it yet.

[Kidd280]

Originally Posted by turbofan

i found them on amazon.

https://www.amazon.com/gp/product/b0...?ie=utf8&psc=1

mine blow often.
Also found 35amp self resetting circuit breaker from another vendor but haven't installed it yet.

👍🏻