Trailer Wiring Weirdness
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Trailer Wiring Weirdness
1993 F-350 Factory towing wiring
When I got this the factory harnesses were not being used. The wire for brake power went directly from the controller to the trailer connector and the turn signals and brake lights for the connector were spliced into the trucks lights wires. There were several blown fuses. I figured that that PO didn't know this and did his wiring as a work around.
I rewired everything using the factory harnesses. I checked my work by probing the trailer connector with a multimeter and every thing checked out fine.
Now when I put it into reverse, the side markers come on. I don't know is this was intended or if something is wrong.
When the engine is running and I use the hazard flashing lights, power to the trailer brakes is applied. The trailer brake light on the controller does not flash with the hazards. I know that this was not intended.
Not having a wiring diagram for the trailer wires, I am at a loss as where to start. Are there wiring diagrams available on line?
When I got this the factory harnesses were not being used. The wire for brake power went directly from the controller to the trailer connector and the turn signals and brake lights for the connector were spliced into the trucks lights wires. There were several blown fuses. I figured that that PO didn't know this and did his wiring as a work around.
I rewired everything using the factory harnesses. I checked my work by probing the trailer connector with a multimeter and every thing checked out fine.
Now when I put it into reverse, the side markers come on. I don't know is this was intended or if something is wrong.
When the engine is running and I use the hazard flashing lights, power to the trailer brakes is applied. The trailer brake light on the controller does not flash with the hazards. I know that this was not intended.
Not having a wiring diagram for the trailer wires, I am at a loss as where to start. Are there wiring diagrams available on line?
Lead Driver
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From: Roseville, MN
First thing I'd do is make sure the trailer is grounded well, and having it hitched to the truck is not grounded well. At least 99% of the electrical gremlins I've chased in automotive wring, but trailer wiring especially, comes back to bad ground connections.
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There is no trailer attached. The symptoms are on the truck only. The factory harness has a 10 gauge white wire for ground. I checked it by attaching a wire directly to the negative battery terminal and it checked good. The fault has to be in the factory wiring/harnesses.
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Very nice. Thank You, subford
Is this off the factory manual on CD?
I found the body/chassis and powertrain/drivetrain manuals at a local bookstore but they don't have much in the way of wiring diagrams. The owner said that there is a separate manual for that. I saw one on eBay for $125. If I was planning on keeping the truck, I'd grab it.
Is this off the factory manual on CD?
I found the body/chassis and powertrain/drivetrain manuals at a local bookstore but they don't have much in the way of wiring diagrams. The owner said that there is a separate manual for that. I saw one on eBay for $125. If I was planning on keeping the truck, I'd grab it.
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More weirdness
To rule out that my work wiring the trailer connector was not the source of the problems, I disconnected the two connectors behind the spare tire that feed the trailer connector.
The side markers turning on when in reverse is in the connector.
The trailer brake power (the light on the controller turns on) still is activated when the warning lights are flashing an the ignition is on. The weird part is that when I pull relay 1 (engine controller per the owners manual), in the under hood fuse/relay box, the light on the controller goes out. None of the other relays affect the fault.
There is another trailer connector in the bed that was used for a fifth wheel trailer. They used Cold Splices AKA Quick Splice Scotchloks, which I don't like, to splice into the factory wiring. I don't think that this could be the source of the problem but I'll check it out.
None of the factory wiring seems to have been touched except the trailer connector splice described above. This is going to be a tough one.
To rule out that my work wiring the trailer connector was not the source of the problems, I disconnected the two connectors behind the spare tire that feed the trailer connector.
The side markers turning on when in reverse is in the connector.
The trailer brake power (the light on the controller turns on) still is activated when the warning lights are flashing an the ignition is on. The weird part is that when I pull relay 1 (engine controller per the owners manual), in the under hood fuse/relay box, the light on the controller goes out. None of the other relays affect the fault.
There is another trailer connector in the bed that was used for a fifth wheel trailer. They used Cold Splices AKA Quick Splice Scotchloks, which I don't like, to splice into the factory wiring. I don't think that this could be the source of the problem but I'll check it out.
None of the factory wiring seems to have been touched except the trailer connector splice described above. This is going to be a tough one.
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It has the 7.5/460 gasoline engine.
I am close to understanding the problem of the trailer brake power coming on with the flashers. That it happens only with the key on confuses the matter. It has to be in the multi function switch. Does page 149-4 have more testing instructions? 149-5?
I am close to understanding the problem of the trailer brake power coming on with the flashers. That it happens only with the key on confuses the matter. It has to be in the multi function switch. Does page 149-4 have more testing instructions? 149-5?
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To make sure sure that the splices described in a previous post were not causing the issue, I disconnected the trailer wire connectors located under the hood. The problem still persists.
I did the test on the pages that subford provided plus some that I made up. Everything checks good.
subford, the drawings have been so helpful, thanks so much. If you are ever in the Pacific Northwest stop by and I'll buy you a beer, hell, I'll buy you a steak diner.
I do have one more request: What does the manual say about the function of relay 1 (closest to the fender) under the hood? The owners manual says engine control but when I pull that relay the flasher/brake power works normally so it must be doing other functions also. The drawing for that circuit would be nice.
I did the test on the pages that subford provided plus some that I made up. Everything checks good.
subford, the drawings have been so helpful, thanks so much. If you are ever in the Pacific Northwest stop by and I'll buy you a beer, hell, I'll buy you a steak diner.
I do have one more request: What does the manual say about the function of relay 1 (closest to the fender) under the hood? The owners manual says engine control but when I pull that relay the flasher/brake power works normally so it must be doing other functions also. The drawing for that circuit would be nice.
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subford
That looks like what I have except my truck has two more relays on the side.
I went to eBay to get CD with electrical diagrams but they don't have any now. Could you burn a CD and mail it to me, please? I'll mail you some money.
I would give up but I can't knowingly sell a truck that has a potently dangerous defect.
The EEC relay must control other things because the flasher/electric brake power works correctly when the relay is pulled. I am starting to wonder if it is a factory defect.
You have been so helpful, I hate impose on you again, but I need to verify that relay 1 has other other uses besides the EEC. Can you look this up and post it?
Thanks so much.
That looks like what I have except my truck has two more relays on the side.
I went to eBay to get CD with electrical diagrams but they don't have any now. Could you burn a CD and mail it to me, please? I'll mail you some money.
I would give up but I can't knowingly sell a truck that has a potently dangerous defect.
The EEC relay must control other things because the flasher/electric brake power works correctly when the relay is pulled. I am starting to wonder if it is a factory defect.
You have been so helpful, I hate impose on you again, but I need to verify that relay 1 has other other uses besides the EEC. Can you look this up and post it?
Thanks so much.