7 Wire trailer wiring - PowerStrokeNation : Ford Powerstroke Diesel Forum
 
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post #1 of 5 (permalink) Old 03-22-2010, 06:18 AM Thread Starter
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Question 7 Wire trailer wiring

Hey guys. My 95 F-250 appears to have all the fuses in the Power Distribution Box needed for wiring up an RV type 7 wire connector but there doesn,t seem to be any continuity to the one harness connector at the rear under the bumper. The 4 wire connector is working. Am I missing something to complete this connection?
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post #2 of 5 (permalink) Old 03-23-2010, 03:51 PM
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Re: 7 Wire trailer wiring

There is a light duty wiring harness and a heavy duty harness. Do you have a factory installed 7 way plug under the back bumper? If not you'll need to change out the rear harness or add wires to it.
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post #3 of 5 (permalink) Old 03-24-2010, 12:41 AM Thread Starter
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Re: 7 Wire trailer wiring

No 7 way plug installed but there are 2 stock connectors available behind the back bumper. One has 4 pins and connects to the stock four wire flat harness that came with the truck. The other has 3 pins but none seem to be powered even with the truck running. I think I may not have the "trailer tow relay" factory installed. Seems kind of odd they would install the fuses but not the relay
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post #4 of 5 (permalink) Old 03-24-2010, 02:27 AM
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Re: 7 Wire trailer wiring

That is odd. I didn't think the light duty wiring had those plugs. Do you have the two relays attached to the firewall next to the brake booster? Those relays are part of the heavy duty wiring that powers that second plug. IIRC, one is reverse, one battery charge, and one brakes. The reverse and battery charge relays are in that relay block I mentioned and the brake plug is under the ashtray in the cab.
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post #5 of 5 (permalink) Old 03-24-2010, 08:45 PM Thread Starter
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Re: 7 Wire trailer wiring

No those relays don,t appear to be there although I do believe I see where the connector for the wiring from the rear bumper terminates under the hood. It terminates right where you said the relays should be. I wonder if Ford still has these relays available?
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