trailer battery not charging

dwhicks

Member
Hello all, first post here. I have a 2011 Ford f150 with the tow package. I am not getting 12 v at my 7 pin plug so the trailer battery is not charging. I have installed the relay and 30 amp fuse required in the power box under the hood, but still no 12v at the 7 pin. Is there another fuse I am missing? All trailer lights work. Any suggestions?
Thanks David
 

Flick

Well-known member
Hello all, first post here. I have a 2011 Ford f150 with the tow package. I am not getting 12 v at my 7 pin plug so the trailer battery is not charging. I have installed the relay and 30 amp fuse required in the power box under the hood, but still no 12v at the 7 pin. Is there another fuse I am missing? All trailer lights work. Any suggestions?
Thanks David

After you hook up the the trailer to your truck, with the engine running, press down on the brakes. On some Ford trucks, it’s the tapping or pressing of the brakes that sends the message to the relay that there is another charging system in the mix. Don’t know if the 2011’s are wired this way or not.
 

dwhicks

Member
Thank you for replying Flick. I tried hooking up, engine running , depressing brake but still no 12v to my 7 pin. also, if it's working properly, should'nt I be able to plug in and run my trailer's 12v electrical from the truck? Even if trailer batteries are dead?
Thanks again for any help
David
 

danemayer

Moderator
Staff member
When you measure voltage at the truck connector, don't forget you need a good ground for the meter. And if there's a problem with the ground path between the truck connector and truck battery, you wouldn't be able to charge the trailer battery.

Does the trailer battery get charged when on shore power?
 

dwhicks

Member
Thanks danemayer. I do not have a volt meter, just a little 12v check light. But I can confirm left and right signal lights and running lights are getting power to their respective pins in the 7 pin connection on the truck. Yes, the batteries get charged when we are plugged in at a campsite.
 

Flick

Well-known member
Thank you for replying Flick. I tried hooking up, engine running , depressing brake but still no 12v to my 7 pin. also, if it's working properly, should'nt I be able to plug in and run my trailer's 12v electrical from the truck? Even if trailer batteries are dead?
Thanks again for any help
David
The truck charging system is there to sustain a good voltage/battery. If your house batteries are not charged, then the truck would probably not charge them up, at least not sufficiently to be able to use them in a normal manner.
 

danemayer

Moderator
Staff member
Thanks danemayer. I do not have a volt meter, just a little 12v check light. But I can confirm left and right signal lights and running lights are getting power to their respective pins in the 7 pin connection on the truck. Yes, the batteries get charged when we are plugged in at a campsite.

It does sound like you have a truck wiring problem of some sort.
 
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