Trailer wiring issue..
Hotshot
Joined: Jan 2004
Posts: 19,760
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From: St Louis
OK thanks. One thing that seems to throw a few people for a loop is, I do not have the fuse block in the engine compartment on the Drivers side wheel well. All that is there is one big relay and two smaller ones and they dont seem to have anything to do with the trailer lighting. I guess I have to look around for another fuse block then huh? In the central junction box (under the dash) is where my fuses are for the trailer lights, constant power etc. I do wish I had the box under the hood, that would make this so much easier..
I hate electrical gremlins, they are tricky little guys...
Thanks
Hab
I hate electrical gremlins, they are tricky little guys...
Thanks
Hab
These relays should both click together when the brakes are applied (or individually when the turn signals are operating). If they are not clicking, then either they lost their common ground connection or the signal isn't getting there from the multi-function switch on the column. The relay's coils are in parallel with the rear stop lamps.
If they ARE clicking, make certain you have checked mini-fuse F2.6 in the passenger compartment fuse box. It supplies power to the normally open contacts of the relays and is supposed to power the trailer stop/turn lamps when the relays energize.
Steve
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Senior User
Joined: Apr 2009
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From: Johnstown PA
Dave and Steve, Thanks. Those are the relays I looked at probably 6 times, and still did not know that. They do click when the appropiate function is performed. I have checked fuse 6 with a meter and it is good too. The fuse gets power also. I still get low voltage at the trailer connection. I did disconnect the trailer brake controller (Reese pod) and had the same results. The one thing I did notice this time around, was that the electric brake (At trailer connection) cycles. What I mean is that the test light, slowly gets bright, goes out, and gets bright again. Is that normal? I am not very educated on how the brake controller/system works.
Thanks again to everyone that is helping me out.
Thanks again to everyone that is helping me out.
Moderator
Joined: Jan 2001
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From: Virginia
The brake voltage does rise up slowly, and the pulsing my be a function of a fancier controller. I only have experience with the cheap ones that rise up slowly till the wheels slide on a empty trailer.
If you could use the diagram, and find the correct color wires around the relays, I would poke them with something sharp and see if you have the correct voltages. You should have 12 volts coming in from the fuse, and that power should blink on and off on the correct wires leaving the relays. If all that works, then it's obvious you have a connection problem between relay box 4 and the rear plug.
If you could use the diagram, and find the correct color wires around the relays, I would poke them with something sharp and see if you have the correct voltages. You should have 12 volts coming in from the fuse, and that power should blink on and off on the correct wires leaving the relays. If all that works, then it's obvious you have a connection problem between relay box 4 and the rear plug.
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Senior User
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From: Johnstown PA
Dave, My controller is an advance auto special (Made by Reese), but that may be its normal operation. Hopefully I can get into the garage tomorrow to check out the underside of the relays to ensure they are getting enough juice. I have it narrowed down to between there, and the harness connection under the truck. Of course, if it is the harness, Thats probably the most difficult one to change....
Thanks
Thanks
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Senior User
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From: Johnstown PA
OK, back at it today. The relays are good, I used the relay ground as the ground and my test light was nice and bright, and blinking at the correct rate. Brakes were good also. I went down to the kickpanel on the drivers side, pulled that off and pulled up the floor trim to undo those bundles. There was all kinds of crud in there, and I thought I may get lucky and find a corroded wire, no luck. So, my new question. One wire loom exits the truck to the connection I followed from the back of the truck, but not all off the wire colors match up (Most importantly, the turns). They, go to another loom just behind it and go under the seat. I could not find under the truck where they exit, and its not making sense to me. Oh, the wires (colors) that exit the relay go into the second loom that go under the seat. I do not have power anything (Seats, windows etc) so where do you think these wires go. My next step I guess is to remove the seat and pull up the vinyl (dont have carpet either) to see.
Any suggestions??
Thanks again
Any suggestions??
Thanks again
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Joined: Jan 2001
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From: Virginia
I have never worked on your newer style truck, but if I was a Ford engineer, and I was going to the rear bumper of the truck with trailer wires, I certainly would not go into the cab with the wires.
Of course I don't have a 4 year degree, and you never know what these guys are thinking, but are you sure it just doesn't run from the relays down to the frame to the rear?
Of course I don't have a 4 year degree, and you never know what these guys are thinking, but are you sure it just doesn't run from the relays down to the frame to the rear?
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Senior User
Joined: Apr 2009
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From: Johnstown PA
You have found relay box #4. The large relay is for your A/C clutch, the two smaller ones are for the trailer turn signals.
These relays should both click together when the brakes are applied (or individually when the turn signals are operating). If they are not clicking, then either they lost their common ground connection or the signal isn't getting there from the multi-function switch on the column. The relay's coils are in parallel with the rear stop lamps.
If they ARE clicking, make certain you have checked mini-fuse F2.6 in the passenger compartment fuse box. It supplies power to the normally open contacts of the relays and is supposed to power the trailer stop/turn lamps when the relays energize.
Steve
These relays should both click together when the brakes are applied (or individually when the turn signals are operating). If they are not clicking, then either they lost their common ground connection or the signal isn't getting there from the multi-function switch on the column. The relay's coils are in parallel with the rear stop lamps.
If they ARE clicking, make certain you have checked mini-fuse F2.6 in the passenger compartment fuse box. It supplies power to the normally open contacts of the relays and is supposed to power the trailer stop/turn lamps when the relays energize.
Steve
If I pull either of these relays, the corresponding light on the truck does not work. Also, If I pull fuse 6 (trailer brake/turn) those relays still "click". So, do those relays do both truck and trailer? I was under the impression that there was a complete seperate system for the trailer, but maybe its just fused seperately?
I did follow those wires down along the firewall (after remove quite a bit of loom covering) to the frame where it meets up with the other plug. So, under the truck (Under drivers seat area) there are two connections, and all the wires from those go into one loom and to the back of the truck (Of course, between frame and fuel tank) So I guess now, I have to get into that loom to see whats what. And to make things worse, my multi-meter gave up the ghost today
. So its a trip for a new one, and maybe another new tool or two while I am at it. Thanks
Hotshot
Joined: Jan 2004
Posts: 19,760
Likes: 1,079
From: St Louis
Removing the relay should NOT affect the truck lights. See my description above for the coils and also for F2.6.
The EVTM shows that the trailer signals do NOT re-enter the cabin.
Steve
The EVTM shows that the trailer signals do NOT re-enter the cabin.
Steve
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Senior User
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From: Johnstown PA
Steve, I will be out there today and will double check. I did find the wires follow the firewall and along frame. F2.6 is good. And the relays in parallel? You will have to excuse my ignorance for wiring.... Can you elaborate for me?
Thanks...
Thanks...
Moderator
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From: Virginia
The coils of the relays are tapped into the truck's turnsignal wires for the rear. So whatever the truck's rear lights are doing, the relays are doing the same thing. That's what all the clicking is about.
Now when the relay clicks, it's moving a set of contacts inside the relay. It's just touching them together, and then breaking them apart. So they feed these contacts with that other trailer fuse. So the trailer lighting is totally separate, but follows the function of the truck's lights. So if you have a problem with the trailer wiring, the trailer fuse blows, but the truck's lights still work.
Now when the relay clicks, it's moving a set of contacts inside the relay. It's just touching them together, and then breaking them apart. So they feed these contacts with that other trailer fuse. So the trailer lighting is totally separate, but follows the function of the truck's lights. So if you have a problem with the trailer wiring, the trailer fuse blows, but the truck's lights still work.
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Senior User
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From: Johnstown PA
Thanks Dave. Didnt get out there today, but like I posted yesterday, I found where the wires go into the single loom now, I am gonna take off the plastic loom to check each wire. One must be corroded/broken in there.
Thanks for the explanation, Electrical stuff has never been my strong suite, Guess I never had to work with it much
Thanks for the explanation, Electrical stuff has never been my strong suite, Guess I never had to work with it much
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Senior User
Joined: Apr 2009
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From: Johnstown PA
Should there be two constant powers? One that is true constant, one constant with the switch on, and then the switched power?
Thanks
Reps to you guys for all your help...
FTE Legend
Joined: Jul 2005
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From: Millersville, MD
I think at this time, I would simply cut the wires coming from the relays( leave enough to solder in new wire) and run an EXTERNAL wire to the trailer plug (maybe attach with alligator clips) and see if the lights work. This should save you much time...if it DOES work, just run new wiring...cheaper and easier than trying to find a break/open circuit/short.