I have a 2017 Jayco Pinnacle 5th wheel pulled by a 2015 F350.The jayco is about 5 weeks old. Took a trial trip in June and noticed that the batteries were a third dis-charged after towing all day. Had the trailer at the dealer and he said- your truck fuse is blown that provides power to the trailer.Well had my mechanic replace the 25 amp fuse and sold my house and left town. The fuse has blown again and I am not sure of where to look as to the root cause. Assume something in the trailer is shorting it out. No option to take it to the dealer since I am hundred of miles away and going south.Not a big deal if I am going to campgrounds, but I've had to dry camp a couple of times overnight and I worry I won't have powerWhat would anyone suggest I do?

Is 25A the proper fuse? I could easily see a large discharged battery bank pulling more power than that. I think GM, for instance, uses a 40 amp fuse. I'm not suggesting you just stick a bigger one in there but I would make sure that's really the correct size. Does it blow right away? If so that would indicate a direct short. If it takes some time later it's likely an overload or a wire that has an intermittent short. Intermittents are difficult to find, you just need to start inspecting the wiring.

Double check the manual. I think mine is 40 amps.

Is 25A the right size fuse? Seems like they're usually 40A?I would verify the size needed and learn how to replace it myself.Also, I would verify that the relay is installed for charging trailer batteries. It may have been missing all this time as Ford doesn't always include it for some reason.

"No option to take it to the dealer since I am hundred of miles away..."If you can't fix it driving back a hundred miles will be less expensive than someone else fixing the problem. One local shake down IMO isn't enough.

Here is the 2015 F350 Owner's Manual. Look at page 223 to 227. Fuse #90 is Trailer Tow Battery Charge 25 amp, so 25 amp is correct.Also#10 is Trailer Tow 40 amp#22 is Trailer Tow Electric Brake 30 amp#26 is Trailer Tow Park Lamps 30 amp#29 is Trailer Tow Park Lamps Relay#70 is Trailer Tow Backup Lamp 10 amp#76 is Trailer Tow Backup Lamp RelaySince the fuse doesn't blow unless you are towing the trailer, my guess is the problem is in the trailer. If the problem was in the truck, the fuse should blow whether you are towing a trailer or not. I would find a Jayco dealer. It sounds like a warranty issue to me.

blowing fuse on power line to trailer | Good Sam Community

Bobbo
Explorer II
Aug 05, 2017
In that case, you may want to run a heavy gauge (10g is OK to 30 amps, 8g is OK to 45 amps) wire from the tow vehicle battery to the hot connector on the truck's 7 pin and use a larger fuse. Be sure to run it through a relay so it is only hot when the ignition is on. If you do this, pull the 25 amp fuse so that wire is not hot any longer.
paulbeauchemin
Explorer
Aug 05, 2017
ScottG wrote:
Since 25A is correct, it may blow when the batteries are low even if everything is fine.
And don't forget about the relay..

I've got a pair of 12v deep cycle batteries. Seems like it has blown after I've done a couple of nights off grid and batteries are low.

When I first hook up to power my EMS is drawing 20 amps with nothing in the trailer on, so I'm thinking that is draw from batteries
MEXICOWANDERER
Explorer
Aug 05, 2017
90% of shorted charge lead wires are inside the pigtail connecting to the truck socket socket or trailer plug. Disconnect, disassemble and look for pulled-loose strands or two connected wires touching each other.
westend
Explorer
Aug 04, 2017
I had an issue with electrical to the trailer. I discovered that the wires to the truck's umbilical socket had been hit by a rock and the copper inside the wire's insulation jacket had parted. I disconnected the plug socket and disassembled it, stripped back to good wire, reassembled and haven't had an issue since. Ford F-250 and F-350 have the trailer plug socket mounted very low.
pianotuna
Nomad III
Aug 04, 2017
The house battery charging circuit in my E-450 was 60 amps. After the 3rd one blew I replaced it with a 50 amp autoreset circuit breaker.
time2roll
Nomad
Aug 04, 2017
Disconnect a battery cable and see if the fuse still opens.
ScottG
Nomad
Aug 04, 2017
Since 25A is correct, it may blow when the batteries are low even if everything is fine.
And don't forget about the relay..
Old-Biscuit
Explorer III
Aug 04, 2017
According to manual the 25A is correct for 'Trailer Tow Battery Charge'

Power Dist Box..engine compartment

#10-----40A Trailer Tow (no other description)
#22-----30A Trailer Tow Electric Brakes
#26-----30A Trailer Tow Park Lamps
#29.....Relay Trailer Tow Park Lamps
#70-----10A Trailer Tow Backup Lamp
#76.....Relay Trailer Tow Backup Lamp

#88------25A Trailer Tow Battery Charge

Blowing fuse...
Need to check wiring on backside of 7 pin receptacle on truck, any extended harness wiring for 2nd receptacle (if you have another one in bed vs on bumper)
Need to check wring on trailer plug
Looking for any bad wiring, wires touching etc

Or plug a different trailer into your trucks 7 pin receptacle and see if fuse blows.
If it does.....problem with truck wiring
If it does NOT.problem with trailer wiring

Only fuse blowing is that 25A battery charge...making contact with ground circuit some where.
Bobbo
Explorer II
Aug 04, 2017
Here is the 2015 F350 Owner's Manual. Look at page 223 to 227. Fuse #90 is Trailer Tow Battery Charge 25 amp, so 25 amp is correct.

Also

#10 is Trailer Tow 40 amp
#22 is Trailer Tow Electric Brake 30 amp
#26 is Trailer Tow Park Lamps 30 amp
#29 is Trailer Tow Park Lamps Relay
#70 is Trailer Tow Backup Lamp 10 amp
#76 is Trailer Tow Backup Lamp Relay

Since the fuse doesn't blow unless you are towing the trailer, my guess is the problem is in the trailer. If the problem was in the truck, the fuse should blow whether you are towing a trailer or not. I would find a Jayco dealer. It sounds like a warranty issue to me.
Lwiddis
Explorer II
Aug 04, 2017
"No option to take it to the dealer since I am hundred of miles away..."

If you can't fix it driving back a hundred miles will be less expensive than someone else fixing the problem. One local shake down IMO isn't enough.