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Ask Kenny Z. Your Own Question
Kenny Z.
Kenny Z., Ford Senior Master Tech
Category: Ford
Satisfied Customers: 5235
Experience:  Auto Trans, Drivability and Electrical Specialist
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I have power to the lights on my trailer but not the power

Customer Question

I have power to the lights on my trailer but not the power jack circuit. Can you tell me which fuse operates that line. My last F-150 was delivered without a fuse in that space so I want to check to make sure this one has one.
JA: Most vehicles have two fuse panels. Have you located both?
Customer: I did a couple of weeks ago but not this morning.
JA: What year is your F-150?
Customer: 2015 F-150 I have the manual and see where the second one is in the lower passenger side foot area.
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I took it to the dealer about two months ago and he said there was power to the trailer. I tested the power line last night before I replaced the power jack, thinking that it failed, and couldn't get a power read on the tester.
JA: Anything else you think the mechanic should know?
Customer: No. I think it is specifically related to which fuse runs the power, not the lights.
Submitted: 4 months ago.
Category: Ford
Expert:  Randall C replied 4 months ago.

Hello, is this a 4x4? what engine? need to be sure I pull correct diagrams, I also assume you have the 7 pin plug and no power to what is called, battery charge pin at the trailer plug

Customer: replied 4 months ago.
I have the larger ecoboost, 4x4. It has the tow package with the seven pin in use for the RV trailer.
Expert:  Randall C replied 4 months ago.

and,, do you refer to the main battery power.charge pin on the plug

Customer: replied 4 months ago.
I don't have power to my jack. The jack power wire doesn't test for power. What fuse provides power to that line?
Expert:  Randall C replied 4 months ago.

well, I own several campers and no separate line to just the jack, It has to be the main power line from truck to trailer that charges a battery on the trailer, My jack works off that battery , yours may be wired to that line, it is possible and likely..so, with this said? you mean no power to battery wire at the plug, that is how all my jacks are wired so,, 2 fuses, both in the under hood fuse box, fuse# ***** and fuse# ***** 21 is a 30 amp fuse and 54 is a 5 amp fuse,I have attached a diagram. now thos fuses are controlled by the body module, hard to explain so really need to swap both of these fuse and see

Customer: replied 4 months ago.
I suspect it is the main power line but I didn't see where any fuse was labeled as such. All that I saw were labeled concerning lighting. I will check those. Thank you
Expert:  Randall C replied 4 months ago.

i promise it is one of those 2 fuses or... another issue which would be hard for me to help with, meaning a wire issue etc, These fuses are in the under hood fuse box, dont just look at them, you need to change both to be sure

Customer: replied 4 months ago.
Your diagram doesn't match my truck
Expert:  Randall C replied 4 months ago.

under hood? correct?

Customer: replied 4 months ago.
Customer: replied 4 months ago.
3.5L V6 Eco
Expert:  Randall C replied 4 months ago.

try this one, fuse #54 is the main fuse

Customer: replied 4 months ago.
That is listed as a 'voltage quality module Body-control-module. That isn't listed as a trailer controller. Do you have something that would make you think that operates that circuit?
Expert:  Randall C replied 4 months ago.

I know how it is listed, i tried to explain the power feed is BCM controlled, I will opt out, open the post to the other experts, I am sorry could not help, Please save the rating for the expert that can help you, thanks

Customer: replied 4 months ago.
No offense. I'm just trying to make sense of it.
Expert:  Kenny Z. replied 4 months ago.

Hello, my name is***** and thanks for your question.

So you are referring to pin 5, 3 o'clock position when looking at the connector from the front (orange wire) has no voltage?

Customer: replied 4 months ago.
It is my opinion that it would be #4 black for 'battery' on a seven pin connector. I want to know what circuit/fuse controls this circuit so that I can verify it is in the circuit box or it is not blown.
Expert:  Kenny Z. replied 4 months ago.

According to my Ford service publications, pin 4 is green, right turn

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