7pin power on all the time?

[vetto]

Went to test my 7 pin connector prior to picking up my new travel trailer tomorrow.
Using a test light, found that +12V charging pin (pin4) is hot with the truck off.
I haven't put a voltmeter on it, but I read somewhere that on some makes, this pin is normally at .2V for sensing a load (like when a trailer gets attached) and then goes to +12. The test light could be seen by the truck as a "load" and that's what I'm seeing?
Seems odd that this pin would be hot all the time with the truck off.

Can someone put a test light on their pin 4 with the truck off and see if it lights?

 

[nc_beagle]

Mine didn't light up. Doors were unlocked, but no key in the truck, if that would matter at all.

 

[Jimmy07]

Went to test my 7 pin connector prior to picking up my new travel trailer tomorrow.
Using a test light, found that +12V charging pin (pin4) is hot with the truck off.
I haven't put a voltmeter on it, but I read somewhere that on some makes, this pin is normally at .2V for sensing a load (like when a trailer gets attached) and then goes to +12. The test light could be seen by the truck as a "load" and that's what I'm seeing?
Seems odd that this pin would be hot all the time with the truck off.

Can someone put a test light on their pin 4 with the truck off and see if it lights?
View attachment 109324

Pin 4 12v+ is always hot on all Ram trucks, as it goes straight to the battery via 30 amp fuse F01. It is pin 2 that detects the trailer being hooked by sensing it’s resistance.

 

[vetto]

Mine didn't light up. Doors were unlocked, but no key in the truck, if that would matter at all.

Pin 4 12v+ is always hot on all Ram trucks, as it goes straight to the battery via 30 amp fuse F01. It is pin 2 that detects the trailer being hooked by sensing it’s resistance.

Um. So "hot or not"?
The more I think about it, it's probably hot all the time since everything else is (brakes, lights when appropriate, etc) regardless of trailer.

That brings me to something that I've also always wondered, what does the "sensing" of a trailer via the 7 pin actually mean? Does the truck do something different when there is a trailer and when there isn't? Maybe start/stop the "Trailer Trip" mileage? That would make sense I guess, but I cant think of anything else meaningful that it could do.

 

[Jimmy07]

Um. So "hot or not"?
The more I think about it, it's probably hot all the time since everything else is (brakes, lights when appropriate, etc) regardless of trailer.

That brings me to something that I've also always wondered, what does the "sensing" of a trailer via the 7 pin actually mean? Does the truck do something different when there is a trailer and when there isn't? Maybe start/stop the "Trailer Trip" mileage? That would make sense I guess, but I cant think of anything else meaningful that it could do.

My response was not a guess. If it is not hot all the time, there is something wrong. Pin 2 on the 7-way is the electric brake feed that goes to the trailer brake module. The trailer’s brake feed circuit has resistance, which the trailer brake module is looking for when you plug in the trailer. The trailer module then communicates to the instrument cluster over canbus to bring up the trailer selection menu to choose which trailer is being used.

 

[vetto]

My response was not a guess. If it is not hot all the time, there is something wrong. Pin 2 on the 7-way is the electric brake feed that goes to the trailer brake module. The trailer’s brake feed circuit has resistance, which the trailer brake module is looking for when you plug in the trailer. The trailer module then communicates to the instrument cluster over canbus to bring up the trailer selection menu to choose which trailer is being used.

make total sense. Thanks Jimmy!

 

[nc_beagle]

Sorry, I probably wasn't reading your question correctly. When you said "always" I thought you meant even with the truck off, like you were worried about battery drain. I didn't have mine on when I tested.

 

[Jimmy07]

Sorry, I probably wasn't reading your question correctly. When you said "always" I thought you meant even with the truck off, like you were worried about battery drain. I didn't have mine on when I tested.

To clarify- even with the truck off, there should be 12v constant power on pin 4 of the 7-way trailer connector on the bumper. If there isn’t, there is an issue.

 

[Rlaf75]

I have one of the 7 pin plug connector adapters that you plug in that the little LEDs light up when you activate them. They are pretty cheap at auto parts stores and I've never had any problems using that to test the receptacles on any of my vehicles

 

[nc_beagle]

To clarify- even with the truck off, there should be 12v constant power on pin 4 of the 7-way trailer connector on the bumper. If there isn’t, there is an issue.

Hmmm. Either I wasn't using my tester correctly or none of mine have power with the truck off. I'll try again. I've pulled my camper with it but have no idea if it charged the batteries since the solar panel probably had them topped off already.

 

[vetto]

Hmmm. Either I wasn't using my tester correctly or none of mine have power with the truck off. I'll try again. I've pulled my camper with it but have no idea if it charged the batteries since the solar panel probably had them topped off already.

With my solar + my truck both charging the trailer battery, it just kept up with the 12V refrigerator on my last trip. Trailer battery never dropped below 12.9 or so. (yes, I traveled with the battery disconnect switch "on" and the fridge running.). Might want to check your 7pin, it doesn't output a lot to the trailer charging circuit, but every little bit helps.

 

[Richard320]

Went to test my 7 pin connector prior to picking up my new travel trailer tomorrow.
Using a test light, found that +12V charging pin (pin4) is hot with the truck off.
I haven't put a voltmeter on it, but I read somewhere that on some makes, this pin is normally at .2V for sensing a load (like when a trailer gets attached) and then goes to +12. The test light could be seen by the truck as a "load" and that's what I'm seeing?
Seems odd that this pin would be hot all the time with the truck off.

Can someone put a test light on their pin 4 with the truck off and see if it lights?
View attachment 109324

I'm late to the party, but...

I just walked out with a Fluke 87 DVOM and checked. No key nearby. Truck has been off for at least 12 hours. 12.47V. It's always hot.

 

[Andymax]

First few times I tested my Pin 4 it was zero volts. After having towed my trailer a few times it then read 12+V. I assumed that there must have been some coating or mold release residue on the pins that got worn away by the 7-pin. If you're getting no voltage, try digging into the pin with your test probe a bit.