BMV 712 mystry reading - power going to Truck?

[Yoda]

Its interesting watching the power usage on my Touch 50 and what the BMV 712 is reading. With everything off (No Solar, No Multiplus. No shore power) I have a 0.7 amp draw. It also reads -7 watt. This must be from the propane sensor and Cerbo GX - parasitic drain. Does this sold correct?

But the real mystery is yesterday I had the truck hooked up to go get my new tires on (idle) and decided to see the charge to the trailer. (solar off ), It was showing a negative drain of 1.2 amps. Even when revved up it was still showing a negative drain as if the truck was not charging. Trailer Battery was at 100% SOC but I am sure the truck battery was not as it has been sitting a while.

Today I checked the truck output and it was 13.2 volts at idle. I don't have a way of measuring amps. I also checked my plug extension and it was good, but have not checked the trailer side (not sure where to check - I guess I could start with the Junction box)

So is it possible the trailer was attempting to charge the truck battery, or at least the batterys trying to equalize when truck was on? Wondering what others see on the monitor when truck is plugged in and on. Remember I have an 04 F350 so it does not have all the smart charging stuff the new ones have.

Just curious on this.

Thanks for any thoughts

Keith

[howson]

Thanks for any thoughts

Very possible given the age of your TV. A battery isolater may be in your future...or just disconnect the power wire (like I did) since the power coming from the truck is negligible anyway.

[ncitro]

Its interesting watching the power usage on my Touch 50 and what the BMV 712 is reading. With everything off (No Solar, No Multiplus. No shore power) I have a 0.7 amp draw. It also reads -7 watt. This must be from the propane sensor and Cerbo GX - parasitic drain. Does this sold correct?

But the real mystery is yesterday I had the truck hooked up to go get my new tires on (idle) and decided to see the charge to the trailer. (solar off ), It was showing a negative drain of 1.2 amps. Even when revved up it was still showing a negative drain as if the truck was not charging. Trailer Battery was at 100% SOC but I am sure the truck battery was not as it has been sitting a while.

Today I checked the truck output and it was 13.2 volts at idle. I don't have a way of measuring amps. I also checked my plug extension and it was good, but have not checked the trailer side (not sure where to check - I guess I could start with the Junction box)

So is it possible the trailer was attempting to charge the truck battery, or at least the batterys trying to equalize when truck was on? Wondering what others see on the monitor when truck is plugged in and on. Remember I have an 04 F350 so it does not have all the smart charging stuff the new ones have.

Just curious on this.

Thanks for any thoughts

Keith

I have had a variety of Fords over the years, including a 2005 that is probably the same vintage as yours. As you suggest it is before all of the smart charging, which should simplify troubleshooting. I would start by checking that current can actually flow from the trailer charge port. I know you said you have voltage there, but it could be phantom through a high resistance connection that drops to nothing when loaded down. Grab a light bulb (ideally 12 or 24 volt) and use a couple jumper wires to connect it to the trailer charge pin and ground. See if it lights, and what the voltage is then. Assuming it lights and you have good voltage then start looking at the trailer end (the junction box in the pinbox is a good place to start), if it does not light, then work your way towards the front from the trailer connection until you find the issue. You should find that the actual seven pin receptacle has a cable plugged into the back of it to make it easy to change. If the pins inside it are corroded you might consider replacing it.

[Yoda]

I have had a variety of Fords over the years, including a 2005 that is probably the same vintage as yours. As you suggest it is before all of the smart charging, which should simplify troubleshooting. I would start by checking that current can actually flow from the trailer charge port. I know you said you have voltage there, but it could be phantom through a high resistance connection that drops to nothing when loaded down. Grab a light bulb (ideally 12 or 24 volt) and use a couple jumper wires to connect it to the trailer charge pin and ground. See if it lights, and what the voltage is then. Assuming it lights and you have good voltage then start looking at the trailer end (the junction box in the pinbox is a good place to start), if it does not light, then work your way towards the front from the trailer connection until you find the issue. You should find that the actual seven pin receptacle has a cable plugged into the back of it to make it easy to change. If the pins inside it are corroded you might consider replacing it.

Thanks Neil
Give me places to start.

[Jlawles2]

Yoda depending on what the charge voltage in the camper is set to and the battery voltage of the camper vs the charge voltage of the truck it is possible that the batteries are equalizing.

You might check into a DC clamp meter or an alternator tester like https://www.toolsource.com/circuit-t...r-p-71212.html Use it on the negative battery cable to the battery to indicate the amount of current charging the battery.

You may want to have the TV battery tested. It may be showing signs of age.