No constant + on trailer plug
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Elder User
Joined: Feb 2008
Posts: 550
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From: N. IL
No constant + on trailer plug
On my 01 F-250 I need the constant positive to give power in order for the trailer brake to work properly. I spent two hours tracing everything last night. I checked the fuses under the hood and in the cab, I used the relay from my fan blower (which works) and never got power to the wire. Any ideas, what am I missing?
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Elder User
Joined: Feb 2008
Posts: 550
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From: N. IL
I believe so, the relay box is empty but I took the one that runs the blower fan and placed it in both spots with no change. One relay is for trailer tow battery charge the other is for 4x4 electronic shift on the fly.
Mountain Pass
Joined: Jun 2005
Posts: 202
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From: Arvada, Colorado
You need a 30 amp fuse in location #16 and a relay in position #39. Both under hood.
Check this if you need more info: https://www.ford-trucks.com/forums/2...l-diagram.html
That supplies the constant 12 volts to the trailer for battery charge and such. Brakes are Fuse #28 and a relay for trailer tow backup in position #38.
Check this if you need more info: https://www.ford-trucks.com/forums/2...l-diagram.html
That supplies the constant 12 volts to the trailer for battery charge and such. Brakes are Fuse #28 and a relay for trailer tow backup in position #38.
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Elder User
Joined: Feb 2008
Posts: 550
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From: N. IL
Thanks for the ideas, I have had the truck running and the key on, no luck.
I put a fuse in the #16 position and it test ok with a test light. I'm not sure which relay position is for the backup lights and which is for the battery charge but I tried the relay in both positions with no change.
Just to ensure my sanity I ran a jumper wire last night and everything works perfectly on the trailer. So the only thing I'm missing now is the constant positive.
I put a fuse in the #16 position and it test ok with a test light. I'm not sure which relay position is for the backup lights and which is for the battery charge but I tried the relay in both positions with no change.
Just to ensure my sanity I ran a jumper wire last night and everything works perfectly on the trailer. So the only thing I'm missing now is the constant positive.
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Elder User
Joined: May 2007
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Thanks for the ideas, I have had the truck running and the key on, no luck.
I put a fuse in the #16 position and it test ok with a test light. I'm not sure which relay position is for the backup lights and which is for the battery charge but I tried the relay in both positions with no change.
Just to ensure my sanity I ran a jumper wire last night and everything works perfectly on the trailer. So the only thing I'm missing now is the constant positive.
I put a fuse in the #16 position and it test ok with a test light. I'm not sure which relay position is for the backup lights and which is for the battery charge but I tried the relay in both positions with no change.
Just to ensure my sanity I ran a jumper wire last night and everything works perfectly on the trailer. So the only thing I'm missing now is the constant positive.
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Thread Starter
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Elder User
Joined: Feb 2008
Posts: 550
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From: N. IL
Checked that. I've located the wire where it comes out of the relay box and goes under the firewall to the back. It has no power coming out of the box. The relay has a good power source to it.
Postmaster
Joined: Jan 2005
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From: Peoria, IL