F250 is not charging RV batteries on the road

[J Maguire]

Starting with simple solutions I thought the fuse in slot 65 might be the problem but no luck. Looking for anything obvious I might be missing here. Fairly new setup for me and it has never charged the batteries going down the freeway. 5 hours driving today no charge was gained. Any ideas? Thxs

[GeoffnCheri]

Tow vehicles are generally inefficient at charging batteries while driving. Can you give more information on what the battery charge was at the beginning of the trip and where they were at 5 hours later?

[jkwilson]

With the trailer hooked up, after holding the brake pedal down, does the truck display the “Trailer Connected” message?

[J Maguire]

Tow vehicles are generally inefficient at charging batteries while driving. Can you give more information on what the battery charge was at the beginning of the trip and where they were at 5 hours later?

I just happened to notice that 3 of 4 lights were showing on the dummy panel when we departed this morning and by the time we arrived 5 hours later the panel read the same. That's the longest tow so far with this setup so it caught my attention today at the campsite. Sorry, nothing more techinical to provide at the moment. It's a two battery setup.

[J Maguire]

With the trailer hooked up, after holding the brake pedal down, does the truck display the “Trailer Connected” message?

Yes. Truck always acknowledges on the dash that the 7 pin is plugged in immediately without having to press brakes; nothing else is necessary for them to marry up.

[Buckskin]

Get a 7 pin tester to test your trailer connection on truck. They make just 7 pin test for few dollars less. One below will test both 4 and 7 pin connections.

https://www.amazon.com/IIT-16687-Bla...%2C189&sr=8-24

[Hokensalem]

Starting with simple solutions I thought the fuse in slot 65 might be the problem but no luck. Looking for anything obvious I might be missing here. Fairly new setup for me and it has never charged the batteries going down the freeway. 5 hours driving today no charge was gained. Any ideas? Thxs

The F-250 has to be in gear before that pin comes hot. Have someone in the cab with it in gear to test at the connector or rig you up a light you can see while you are sitting in the seat. My truck keeps the batteries in my TT charged good. I have 2 alternators on my vehicle so that probally make a differance.

[jmbopp]

Besides the fuse there is also a relay in the trucks charging circuit.

[jkwilson]

Yes. Truck always acknowledges on the dash that the 7 pin is plugged in immediately without having to press brakes; nothing else is necessary for them to marry up.

I’m pretty sure the 19 requires you to apply the brake for 3 seconds before charging begins, so if you test the voltage be aware that it could require brake application. Things change from year to year though.

Monitor voltage with a meter on the battery terminals of the trailer. Have someone start the truck, close the door, put it in gear, apply the brakes or whatever else it takes to begin charging. You should see a voltage increase on the trailer battery. Any increase at all shows the system is working.

[J Maguire]

The truck bed 7 pin plug was installed when I bought the RV, the original 7 pin plug in the bumper is not being used currently, I have several things to check out there. Would they use the same fuse?