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External Battery To Power Trailer Jack With 12V Pin On Trailer Connector Of Ford Flex


I have a few questions. I have a 2017 ford flex. I noticed that the + terminal from my vehicle links to a black wire at my trailer connector and feeds the negative side of the battery for my electric break emergency switch and the - terminal from my vehicle links to a white wire at my trailer connector and feeds the positive terminal of the battery for my electric break emergency switch? The battery reads 12.46v from + to - battery terminals on the battery with the trailer disconnected, so it is obviously being charged. Curious as to why this is the case. I could never get any voltage reading at the + terminal at my vehicle, however it does power the jack when in operation I had the emergency battery disconnected, to make sure it was not being used as a source. I assume the vehicle has current sensing and limiting to turn on the power to this terminal, which is why my meter saw nothing? The wire gauge at the vehicle jack + terminal and - terminal is much smaller than the wiring on the trailer side so I doubt that it can deliver much current. Trying to find info on my vehicle side has been a pain. The issue is that when using the jack, it seems to run fairly well with no real load, but when loaded it seems to run out of juice? It lifts the trailer up, but since I am using a weight distribution hitch, I need to raise the vehicle up higher than normal in order to get the sway bars in place. Using the original RAM hand jack rated at 2,000 lbs was not an issue I could even lift the rear of my vehicle off the ground, so I would assume the 3500 lb electric jack should be able to do it easily. But, before it gets to the point I need it to, it acts as though it cant get enough current and it stops. The plastic motor housing did not feel warm. So, assuming that my vehicle cannot proved the current needed and hence need an external battery in order to get enough current to get full power. Based on that, what size battery would I need to deliver enough current and have enough reserve to do it several times without a charge? My trailer is a cargo and it has an extended v-nose so there is not much room to mount a batter box between the v-nose and the jack. A side note. I bought this jack last winter and was not able to install it until this past week. When taking it out of the box, the plastic housing was damaged. The box was not noticeably damaged but the foam under the jack plate was so thin that it was cut out from an impact and it allowed it to push up and tear the side screws of the motor cover case out of place, crack the plastic bottom of the case and it broke one of the plastic screw standoffs off. I disassembled it and was able to epoxy it and use washers between the side casing screws as the screws had pulled through the plastic under impact. The motor control works but the LED light is not working. I made sure all the faston connectors were good and even soldered the wires that had pulled out under impact. Everything ohmed out fine so I know the connections are good. I noticed that you have a case for this as a part. It would be nice to have a replacement sent at no charge along with the switch and LED assembly as one or the other is defective. The LED pcb has no mounting area that I could find and so it appears to just use the wires to hold it in position? Seems odd. I aready have a lot of time vested in it but I am willing to replace the parts myself since I did not install it right away as planned. I have purchased a fair amount of items over the last few years from etrailer. This email is linked to my account if you would like to verify my purchases. I look forward to hearing back and for any help and compensation you can provide me. I would like to remain a faithful and returning customer.


Expert Reply:

It sounds like you have a breakaway kit with a built-in charger. The power wire from the positive side of the battery in your Flex to the trailer connector should feed the positive side of the breakaway battery. The ground should be attached the negative side of the breakaway battery. The built in charger refuels the battery when you have the trailer connected. I attached a diagram of the pin positions of the 7-way on your vehicle. The 12V pin should be feeding the positive side of the breakaway battery.

If you are not getting 12V at the circuit on the 7-Way and you have a factory towing package then it may not be active unless a trailer is connected. This is very common with Ford towing packages.

You definitely shouldn't be having an issue lifting the rear of the Flex with the Electric Jack w/ Footplate part # EJ-3520-BBX which is rated for 3,500 lbs. The jack draws 23 amps so you will need a 12V 30 amp hour battery on the trailer either trickle charged by the 7-Way or a charger like part # CTEK56353.

The plastic casing is replaceable with part # EJ-3520-BCV and the lighting board is replaceable with part # EJ-3520-LT. It could also be the jack ground as well, these jacks ground through the mounting hardware so you want to make sure the mounting hardware is touching needs to be clean and paint free.

expert reply by:
Heather A

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