Will trailer draw power from tow vehicle?

[Ksh-JAY]

Just picked up my trailer from storage, battery was on e. Towed it home 20 minutes, turned on the fridge. Will the trailer draw power from the truck battery while it's plugged into the truck and parked? I have the seven pin plug.

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[Gegrad]

Yes it will. If parking hitched overnight and not connected to shore power, you will want to unplug it from your TV to keep from draining your TV battery.

 

[MattHelm21]

Many newer tow vehicles interrupt power to the 7 pin connector when the ignition is turned off so check your owners manual or use a multimeter to verify output.

 

[chuckster57]

Many newer tow vehicles interrupt power to the 7 pin connector when the ignition is turned off so check your owners manual or use a multimeter to verify output.

Even older ones. My ‘94 doesn’t send any voltage to my trailer unless the key is in the “run” position.

 

[PARAPTOR]

Today just changed 7 pin connector on TV, do not ask Constant 12v Power to 7 pin connector even with key off.

 

[Desert185]

Today just changed 7 pin connector on TV, do not ask Constant 12v Power to 7 pin connector even with key off.

Same with mine.

 

[MattHelm21]

So... Maybe its a Ford thing?

 

[Ksh-JAY]

I have a 2018 ram 2500. I don't recall seeing this in the manual. I can check with a meter in the morning.

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[Rhagfo]

Well our 2001 Ram does feed with ignition off, and it saved me one night. Had drawn down the 5ers battery during the day doing setup, and about 2:00 am the propane alarm went off, no odor. Not sure if converter was bad or without power, connected to TV and all good. Fixed missing missing leg of 50 amp next day.

 

[B-O-B'03]

Our 2013 F150 does not supply power unless the key is on.

And... I found out that Ford does not install the fuse or relay for the trailer circuit, that is supposed to be done by the dealer.

I found the fuse and relay, in a bag in the glove box, while researching why the truck was not providing power to the camper.

YMMV

-Brian

 

[ctbruce5]

Just keep on mind that the gauge of the charge wire from TV to trailer is large (small wire). You won't get a lot of current if you are trying to charge an empty battery.

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[JRTJH]

All Ford trucks equipped with a "factory installed 7 pin connector" have an ignition controlled relay that will not allow the tow vehicle to supply power to the battery charge line in the 7 pin connector unless the ignition switch is turned ON. This was true with my 1987, 1989, 1993, 1995, 2005, 2010, 2013 and 2015 Ford trucks. Some other manufacturers have this feature, some trucks don't.

For me, it's a great thing because it prevents the possibility of a dead truck battery after stopping for an evening. It was even more critical when the trailer had a 12 volt refrigerator or someone left lights on in the trailer (back when they were all incandescent). Back when (before Ford made the change) parking for a couple hours and not realizing that the refrigerator was on or that a kid (or forgetful self) left the bathroom light on, could mean finding someone with jumper cables before you could get back on the road.

 

[JRTJH]

...I found out that Ford does not install the fuse or relay for the trailer circuit, that is supposed to be done by the dealer.

I found the fuse and relay, in a bag in the glove box, while researching why the truck was not providing power to the camper.

YMMV

-Brian

It's been that way with the F150 since 2005. The SuperDuty trucks do come with the fuse and relay installed in the underhood fuse panel.

 

[kjohn73]

Neither our 2013 nor 2015 F150's will feed the RV if the ignition is off. My old 1997 Suburban was the cat's meow. It is a gasser, but with two batteries. The second battery has a dead man's switch. At night, I would kill the connection to the second battery, so always had starting power. Our Cougar 21RBS has two big 12v batteries.

 

[chuckster57]

It's been that way with the F150 since 2005. The SuperDuty trucks do come with the fuse and relay installed in the underhood fuse panel.

Just rolled 2 units to customers that had brand new super duty’s. Neither one had an active charge line. Maybe it’s an Eastern/Mid West thing.

 

[Javi]

Just rolled 2 units to customers that had brand new super duty’s. Neither one had an active charge line. Maybe it’s an Eastern/Mid West thing.

I don't think you will find any late model Ford that will supply power to the trailer with the key in the off position.. It would be a poor choice since it would drag the starting battery down..
The Ford's come with a charging relay and it is generally the dealer's responsibility to install it. I've found it to be about 50/50 that they actually do it.. I've purchased 3 F-series since 2011 and on the first I found the relay in a bag in the glovebox, with the 2012 the dealer told me it was in the glove box if I wanted to use it.. the 2015 dually.. the dealer installed it without being asked..

Javi

 

[JRTJH]

Maybe they changed the process since my trucks were built ??? Who knows? All of my superduty trucks (99, 13 and 15) had the fuse/relay installed and none of my F150's (98, 05 and 10) had them installed, they were all in a package in the glove compartment...

Another possibility: The 17 and newer trucks use the SYNC system instead of the Ford My Touch system. On my truck, when I hitch a trailer and plug in the 7 Pin connector, the truck recognizes that "a trailer" (could be any trailer) is connected. There is a process in the truck computer to name specific trailers if desired. This allows tracking of specific trailers in the truck's computer system. But the truck will provide power to any trailer with a 7 pin connector that's plugged in.

On the new trucks, (as I understand it from the dealer) the truck will not recognize that a trailer is connected until the trailer is "registered in the computer", so maybe it's a "SYNC" thing rather than a "fuse" thing ????
Apparently, the truck will not provide power to the trailer battery until the brake lights have been activated by pressing the brake pedal which lights the trailer brake lights, establishing that a trailer is present and allows the truck computer to turn on power to the trailer.....

Trucks are getting more and more complex. When you have to "introduce the trailer to the truck" so they can talk to each other.... It's more complex than this old man wants my truck to be......

 

[MarcS]

Ford trucks will recognize the trailer regardless if the trailer is input in the dash cluster. The reason Ford allows you to put your trailer in the dash, is they know people haul different trailers. You can set up trailer braking for multiple trailers within the dash. Pick the trailer, and you're set. I set up my TT and pontoon boat. Most people don't know that option exists and have trailer braking set to low and the trailer brake controller set all the way to 10. Customers bring vehicles in all the time saying the don't have trailer brakes. Ford's have 3 setting for the trailer brake controller. Low, medium, and high.

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[JRTJH]

My 2015 F250 had the capability for "me" to name up to 5 trailers in the towing section of the truck's computer. I've got four set up: the Cougar, my boat trailer (no brakes), the flatbed I tow my tractor on and my dump trailer. Selecting the trailer will, as MarcS says, automatically adjust the brake control to that trailer, pull up the mileage "memory" for how far that trailer has been towed and apply power to the trailer charge circuit.

This is somewhat different on the "newer trucks". Apparently the truck won't apply power to the charge circuit until the trailer is "introduced to the truck" by tapping the brake pedal to illuminate the trailer lights. I don't know if this is a "one time, first time" requirement or if it's every time the trailer is connected to the truck via the 7 pin connector....

Here's the comment from the Ford Owner's Manual.

*Your vehicle must recognize the trailer before the trailer can receive power.
Recognizing a Trailer
1. Attach the trailer and wiring connector to your vehicle.
2. Switch on your vehicle.
3. Press the brake pedal for a few seconds.
A confirmation message appears in the information display

My truck (a 2015 "dumb truck") doesn't require this action, it automatically applies power to the trailer charge circuit and I have to manually select which trailer is connected, or I can ignore selecting the trailer and it will "track the last trailer selected". I don't know if the "new trucks" automatically select the trailer or if they just don't apply power until after the brake pedal is pressed.....

Anyway, the general concept that (at least in Fords) power to the trailer charge line is disconnected with "key off" and connected with "key on" has been the way they are wired since at least 1993 (the first one I remember for sure disconnected power with the key off).

 

[Javi]

My 2015 F250 had the capability for "me" to name up to 5 trailers in the towing section of the truck's computer. I've got four set up: the Cougar, my boat trailer (no brakes), the flatbed I tow my tractor on and my dump trailer. Selecting the trailer will, as MarcS says, automatically adjust the brake control to that trailer, pull up the mileage "memory" for how far that trailer has been towed and apply power to the trailer charge circuit.

This is somewhat different on the "newer trucks". Apparently the truck won't apply power to the charge circuit until the trailer is "introduced to the truck" by tapping the brake pedal to illuminate the trailer lights. I don't know if this is a "one time, first time" requirement or if it's every time the trailer is connected to the truck via the 7 pin connector....

Here's the comment from the Ford Owner's Manual.

*Your vehicle must recognize the trailer before the trailer can receive power.
Recognizing a Trailer
1. Attach the trailer and wiring connector to your vehicle.
2. Switch on your vehicle.
3. Press the brake pedal for a few seconds.
A confirmation message appears in the information display

My truck (a 2015 "dumb truck") doesn't require this action, it automatically applies power to the trailer charge circuit and I have to manually select which trailer is connected, or I can ignore selecting the trailer and it will "track the last trailer selected". I don't know if the "new trucks" automatically select the trailer or if they just don't apply power until after the brake pedal is pressed.....

Anyway, the general concept that (at least in Fords) power to the trailer charge line is disconnected with "key off" and connected with "key on" has been the way they are wired since at least 1993 (the first one I remember for sure disconnected power with the key off).

My 2015 F350 XL is even dumber than yours... it don't know nothing about the trailer except connected/not connected..