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Factory 7-Wire Trailer Connection Problem

8 messages,  Last post on Jun 10, 2009 at 2:23 PM

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#1 of 8 Factory 7-Wire Trailer Connection Problem by buffalojoe Jun 07, 2009 (11:47 am)
I have a 1999 Expedition with the factory 7-way trailer connector and I want to pull a 1965 Shasta '20' trailer. When I connect the trailer to the Expedition and test the wires, only the running lights and trailer brakes work correctly. When I turn either turn signal on, both tail lights of the trailer blink. When I put on the brakes, I hear the trailer brakes themselves (controller wired in) but I don't get brake lights. I don't have this problem with my '86 F250. I double-checked the wiring to be sure the trailer matches the Expedition. The only trailer wire not connected is for the brake lights because I thought the turn signal/stop combination would take care of it. Any ideas? Thanks much!
#2 of 8 joe by alwaysfords2 Jun 08, 2009 (4:53 am)
You probably need the brake wire connected. The brake and blinker circuits are connected. When you have a blinker on and step on the brake, the brake light on the blinking side doesn't work. Not sure why something like this would work on a different truck, it doesn't make sense to not have the brake wire connected. Replies to this message: buffalojoe (Jun 08, 2009 8:10 am)
#3 of 8 Re: joe [alwaysfords2] by buffalojoe Jun 08, 2009 (8:10 am)
Replying to: alwaysfords2 (Jun 08, 2009 4:53 am) Thanks for the reply. There's only the one brakelight wire in the trailer plug. Do you think I would need to split that and connect a lead to each of the turn signal/brake connections? There isn't a separate brakelight connector on the Expedition side.
#4 of 8 Joe by alwaysfords2 Jun 08, 2009 (8:57 am)
I just looked up the wiring diagram for a 7 pin trailer. There is no seperate brake wires as you pointed out. A separate run for each blinker/stop combination.   Are you sure the loose wire isn't a ground or something?A bad ground will throw a lot of stuff off.   Take a look, maybe this will help you out http://www.etrailer.com/faq_wiring.aspx Replies to this message: buffalojoe (Jun 08, 2009 9:31 am) buffalojoe (Jun 10, 2009 10:37 am)
#5 of 8 Re: Joe [alwaysfords2] by buffalojoe Jun 08, 2009 (9:31 am)
Replying to: alwaysfords2 (Jun 08, 2009 8:57 am) That diagram is fantastic, thanks for passing it along. The more I look and think about the wiring diagrams, and the more I think about what happened, I will double-check the ground. It may not be loose in the plug but it sure might be loose somewhere else. Talking about chasing gremlins! I'll have to wait until after work to check it all out but thanks again. I'll let you know. Replies to this message: buffalojoe (Jun 10, 2009 10:37 am)
#6 of 8 Re: Joe [buffalojoe] by buffalojoe Jun 10, 2009 (10:37 am)
Replying to: buffalojoe (Jun 08, 2009 9:31 am) The problem is fixed. A fuse had blown in the circuit for the 12V charging line to the trailer battery. It didn't affect the interior lights but that was the missing link for the external lights. Once I put a new fuse in the prongs, it worked fine.
#7 of 8 Cool by alwaysfords2 Jun 10, 2009 (12:19 pm)
Quick and easy fix. Best kind. Replies to this message: buffalojoe (Jun 10, 2009 2:23 pm)
#8 of 8 Re: Cool [alwaysfords2] by buffalojoe Jun 10, 2009 (2:23 pm)
Replying to: alwaysfords2 (Jun 10, 2009 12:19 pm) Thanks for your input, it was much appreciated.

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