Trailer Tow Reverse Lamp Relay
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Trailer Tow Reverse Lamp Relay
I'm looking to add two back-up lights to my 2003 F250. I want to tap into the trailer tow reverse lamp circuit at the rear of the truck but I also want to be able to turn on the two lights without having the truck in reverse thru a switch. I want to tie in to the trailer tow reverse lamp relay coil and supply power to it thru the added switch.
I see in the 2003 Wiring Diagram book that the 6.0 uses a reverse lamp relay powered by the PCM to turn on the standard tail light reverse lamps AND power a "Trailer Tow Reverse Lamp" relay that activates the trailer reverse lamps.
The mystery to me is where to find the trailer tow reverse lamp relay. The diagrams show it as part of the Central Junction Box but it does not call it out specifically with a location? Is it just a "vertual" relay that doesn't really exist?
Any insight would be great. Thanks in advance.
Steve
I see in the 2003 Wiring Diagram book that the 6.0 uses a reverse lamp relay powered by the PCM to turn on the standard tail light reverse lamps AND power a "Trailer Tow Reverse Lamp" relay that activates the trailer reverse lamps.
The mystery to me is where to find the trailer tow reverse lamp relay. The diagrams show it as part of the Central Junction Box but it does not call it out specifically with a location? Is it just a "vertual" relay that doesn't really exist?
Any insight would be great. Thanks in advance.
Steve
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I just looked up the wiring, and realized this relay is built into the fuse box just like the trailer running light relay is. There have been 2 or 3 people on here who have had the running light relay go bad, and found out Ford's fix is to replace the whole fuse box. We came up with a way to add a relay to bypass the internal one, and one local Ford dealer actually did that after he showed them our solution instead of replacing the whole fuse box.
The signal for the backup lamps goes though the digital range switch(if you have an automatic) on the side of the tranny. The wire that comes out to feed the backup lights is a black/pink wire. This wire feeds the backup lamps and the reverse trailer relay both, but the branch is internal to the fuse box, so I don't think you are going to be able to seperate this function out, and be able to run the reverse trailer relay without the regular backup lamps functioning also.
Of course you can do all this if you want to add a relay and not use the reversing trailer circuit.
The signal for the backup lamps goes though the digital range switch(if you have an automatic) on the side of the tranny. The wire that comes out to feed the backup lights is a black/pink wire. This wire feeds the backup lamps and the reverse trailer relay both, but the branch is internal to the fuse box, so I don't think you are going to be able to seperate this function out, and be able to run the reverse trailer relay without the regular backup lamps functioning also.
Of course you can do all this if you want to add a relay and not use the reversing trailer circuit.
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Dave,
Thanks for the information.
I understand what you are saying about the the trailer tow reversing lamp relay coil activation being internal to the fuse box, which makes sense, but I wonder if that has changed on my 2003.
The reason I say that is in the 2003 Wiring Diagram book it shows a black/pink wire leaving the C270g (pin 1) connector, which is the regular reversing lamp relay, and entering the the C270f (pin 1) connector to the trailer tow reversing lamp relay. The regular reversing lamp wire then leave the box thru the C270j (pin 10) connector as a black/pink wire to the normal reversing lamps while the trailer tow reversing lamp wires leave C270j (pin 7) thru a black/light green wire. Sorry for the wordyness.
I'll pull the fuse box and take a look to see if a black/pink wire is truly running into the
C270f connector.
Why Ford would not have used an Auxiliary relay box is beyond me. What would that have cost compared the the price of the truck, not much.
I'll report back on what I find. Again, thanks for your help and information.
Steve
Thanks for the information.
I understand what you are saying about the the trailer tow reversing lamp relay coil activation being internal to the fuse box, which makes sense, but I wonder if that has changed on my 2003.
The reason I say that is in the 2003 Wiring Diagram book it shows a black/pink wire leaving the C270g (pin 1) connector, which is the regular reversing lamp relay, and entering the the C270f (pin 1) connector to the trailer tow reversing lamp relay. The regular reversing lamp wire then leave the box thru the C270j (pin 10) connector as a black/pink wire to the normal reversing lamps while the trailer tow reversing lamp wires leave C270j (pin 7) thru a black/light green wire. Sorry for the wordyness.
I'll pull the fuse box and take a look to see if a black/pink wire is truly running into the
C270f connector.
Why Ford would not have used an Auxiliary relay box is beyond me. What would that have cost compared the the price of the truck, not much.
I'll report back on what I find. Again, thanks for your help and information.
Steve
Last edited by skoveng; Feb 24, 2009 at 07:13 AM. Reason: content
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I pulled the fuse box this afternoon and scoped out the C270f connector and there is a wire, black/pink running into pin 1. I used a quick splice to connect a wire into it (I will remove the quick splice, strip the insulation and solder the wire in later) as a test. It works!
I attached a test light to the center pin of the seven way trailer plug; In reverse the test light lit. I put the truck in park and applied +12V to the wire I installed and the test light lit.
Next I'll tap into the customer access circuit for my +12V to run the hot to my back-up switch, then I'll wire in a water-proof plug to the wires at the back of the truck then wire up the back-ups.
Thanks for your help!
I attached a test light to the center pin of the seven way trailer plug; In reverse the test light lit. I put the truck in park and applied +12V to the wire I installed and the test light lit.
Next I'll tap into the customer access circuit for my +12V to run the hot to my back-up switch, then I'll wire in a water-proof plug to the wires at the back of the truck then wire up the back-ups.
Thanks for your help!
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