Trailer Light/Brake Wiring
05-13-2007, 10:37 PM
#1
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Trailer Light/Brake Wiring
hey guys I need to get my truck wired for towing I was gonna go with 7 pin (tell me if thats the best idea) and I need to throw in the trailer brake thats on the workbench. Isn't there a brake connection under the dash somewhere? I'll prolly need to run wires back there because I don't see any. Any advice?
05-13-2007, 11:21 PM
#2
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The absolute best way is to ignore any factory installed towing packages, as they aren't big enough for more than a couple of lights.
Wire the trailer lights through a switch/wire totally their own.
Wire the brake controller DIRECT to the trailer plug.
Left and right turn will have to be tapped under the bed somewhere, usually near the tail-lights.
Left and right turn are the only factory wires that you should tie anything for the trailer into.
Establish a real clean, easily maintained ground point on truck and trailer; CLEAN IT REGULARLY.
Use big fat wire.
12AWG for left and right turn.
10AWG for ground, lights, and brake.
Go ahead and wire any AUX for future add-ons.
If you will be towing mostly cattle trailers and flat-beds, go with a standard SIX-PRONG plug; as, most trailers of these types will be equipped accordingly.
For some reason, the fifth-wheel camper crowd tends to use predominantly seven-way; the catch there is that about a dozen non-interchangable seven-way plugs exist.
Whichever route you go, be sure to tie in a plain old flat plastic four-way plug, hanging near the rear bumper, for the bejillion utility trailers that are equipped thus.
You can just cheap it and tie into the truck wiring; but, you will be among the millions that are constantly having trailer wiring issues.
Do it right the first time and it will always be right.
Wire the trailer lights through a switch/wire totally their own.
Wire the brake controller DIRECT to the trailer plug.
Left and right turn will have to be tapped under the bed somewhere, usually near the tail-lights.
Left and right turn are the only factory wires that you should tie anything for the trailer into.
Establish a real clean, easily maintained ground point on truck and trailer; CLEAN IT REGULARLY.
Use big fat wire.
12AWG for left and right turn.
10AWG for ground, lights, and brake.
Go ahead and wire any AUX for future add-ons.
If you will be towing mostly cattle trailers and flat-beds, go with a standard SIX-PRONG plug; as, most trailers of these types will be equipped accordingly.
For some reason, the fifth-wheel camper crowd tends to use predominantly seven-way; the catch there is that about a dozen non-interchangable seven-way plugs exist.
Whichever route you go, be sure to tie in a plain old flat plastic four-way plug, hanging near the rear bumper, for the bejillion utility trailers that are equipped thus.
You can just cheap it and tie into the truck wiring; but, you will be among the millions that are constantly having trailer wiring issues.
Do it right the first time and it will always be right.
05-13-2007, 11:41 PM
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What Bearkiller says.
Make sure of grounds.
use adequate wire size.
wire the controller to brake switch and run adequate wire to the connector
I have successfully used a commercially available kit that plugs into the harness where the tail lights plug in. - That gives me a flat four pin for turn, brake and running lights.
Future mods include running that four pin into a set of relays. The hope is to isolate the trailer electrical from thre truck's. This prevents you from hitching to someone's poor trailter wiring.
Over the 30+ years towing RV's, I have found that as Bearkiller states, keep the grounds clean. I also check my plugs and connectors every time I hitch up. Annually, I dissasemble the plug on the truck and clean the corrosion that seems to start to build every winter.
Best wishes.
Make sure of grounds.
use adequate wire size.
wire the controller to brake switch and run adequate wire to the connector
I have successfully used a commercially available kit that plugs into the harness where the tail lights plug in. - That gives me a flat four pin for turn, brake and running lights.
Future mods include running that four pin into a set of relays. The hope is to isolate the trailer electrical from thre truck's. This prevents you from hitching to someone's poor trailter wiring.
Over the 30+ years towing RV's, I have found that as Bearkiller states, keep the grounds clean. I also check my plugs and connectors every time I hitch up. Annually, I dissasemble the plug on the truck and clean the corrosion that seems to start to build every winter.
Best wishes.
05-14-2007, 07:44 AM
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Trailer wiring does not have to be scary. I have done a lot of electrical wiring, house, electronic sound and stereo and automotive, and have settled on some personal "rules" that have worked for me. I suspect you all know most of this, but maybe there will be one tip worth remembering.
The factory Dodge wiring is adequate when new for a basic utility trailer with a simple pair of tail lights - you can tie in most anywhere. For ANYthing more, brakes, extra running lights, break-away battery charge, aux power, etc you need to provide more electrical power - amperage - to the rear. I have spent my life in one snow belt or another, so have come to plan on the annual corrosion season - plays havoc with sheet metal and wire connections.
The problem lies in the fact that our rigs are 15 or so years old, and switches and contacts age and corrode, and become less and less able to carry the needed load over time. I have fried several factory headlight switches, even one factory dash amp gauge by pulling what should have been normal loads.
Scotch-locs, crimp ons, and wire nuts will get you going in an emergency, but none of them have any real life expectancy. (I keep a few in the glove box for emergency, but if I use them, I replace them asap.)
If you are wiring for a large trailer or camper with lights and auxiliary power feeds, you have to plan for the anticipated loads - check your manuals, and instructions, and don't scrimp on wire gauge. If there is ever any question use at least the next heavier gauge (smaller number) wire.
Get a good 7 blade RV receptacle, go to NAPA or similar store and pick up a length of cable (truckers use it all the time- if your counter person doesn't have it, go somewhere else), 7 conductor, 12 & 14 awg wire sizes minimum, it is also available with 10 and 12 gauge wires. A reg cab truck needs about 22 feet, it costs about a "buck-plus" a foot, but it is worth every penny and get a couple feet extra - it's easier to cut off excess than to add more.
If you don't have access to at least a budget soldering gun, do yourself a favor and get one. SOLDER your joints: scotch-locs will work fine - if you only want things to work reliably for a couple months.
Also buy NAPA glue coated heat shrink tubing - it will shrink down to a water/corrosion proof seal - the 8 inch piece of 2" for the connection at the receptacle is also a couple bucks a foot - but worth every penny!
Run the cable from the rear of the truck up under the hood. Tie into your wire harness from the bundle coming out through the firewall. Find each "feeder": left turn, right turn, parking lights, etc. Use each feeder to activate a 30 amp relay (don't use auto-zone or Pep Boys relays here - they are overrated) from NAPA. Keep all your connections in as orderly a fashion as possible, all under the hood, away from road salt, water and gravel. Your connections will last longer, and a roadside repair (or any maintenace for that matter) can be done standing next to the fender, not under the truck in the dark.
This way, each required signal at the receptacle is fed through the relay, the power is provided directly from the battery (through an inline fuse).
Wire up like this and you will never overtax your factory switches, you will always have enough amperage at the tail end, and a power problem (i.e. short, etc) will not take the whole truck down - it will simply blow its individual fuse.
To take this all one step further, you should wire your headlights through relays - use the existing power to each beam to activate the relay, feed the power to the bulbs through the relay through an inline fuse from the battery.
Basic rules:
* use inline fuses for everything
* feed each circuit through relays
* solder - don't crimp or wire-nut - your connections
* use good glue lined heat shrink tubing
* take the time and spend the few extra dollars for good quality wires and cables and plugs
* be sure to use wire sized to the needed load (and then some)
* keep circuits the right color - you will be happy for that 3 years later when you are tyring to trace something out
* don't count on the ball or 5th wheel hitch to conduct your ground - run a wire through the connector
* if you do it right, you only have to do it once
Time spent now while the weather is nice will transform trailer wiring from an annual or monthly frustration into a reliable system that will always be there when you need it.
There are some basic color schemes, and standard wiring configuarations to be found with simple web searches. The wiring diagram is printed right on most good relays. Your trailer brake adapter will always come with wiring instructions when new, can often be found on the web if you bought it used.
One last tip.
I intentionaly "miswire" my trailer connectors. On my trucks the wire normally used for running lights is connected to the trailer brakes, and vise versa. This makes my trailers un-stealable. Anyone else hooks up to one of my trailers, turns on their lights, and the trailer brakes lock up. If anyone else wants to borrow a trailer, I honestly tell them that the wiring is incompatable with their truck and so I am unable to loan it out. (I made up an adapter plug cable so I can borrow theirs)
The factory Dodge wiring is adequate when new for a basic utility trailer with a simple pair of tail lights - you can tie in most anywhere. For ANYthing more, brakes, extra running lights, break-away battery charge, aux power, etc you need to provide more electrical power - amperage - to the rear. I have spent my life in one snow belt or another, so have come to plan on the annual corrosion season - plays havoc with sheet metal and wire connections.
The problem lies in the fact that our rigs are 15 or so years old, and switches and contacts age and corrode, and become less and less able to carry the needed load over time. I have fried several factory headlight switches, even one factory dash amp gauge by pulling what should have been normal loads.
Scotch-locs, crimp ons, and wire nuts will get you going in an emergency, but none of them have any real life expectancy. (I keep a few in the glove box for emergency, but if I use them, I replace them asap.)
If you are wiring for a large trailer or camper with lights and auxiliary power feeds, you have to plan for the anticipated loads - check your manuals, and instructions, and don't scrimp on wire gauge. If there is ever any question use at least the next heavier gauge (smaller number) wire.
Get a good 7 blade RV receptacle, go to NAPA or similar store and pick up a length of cable (truckers use it all the time- if your counter person doesn't have it, go somewhere else), 7 conductor, 12 & 14 awg wire sizes minimum, it is also available with 10 and 12 gauge wires. A reg cab truck needs about 22 feet, it costs about a "buck-plus" a foot, but it is worth every penny and get a couple feet extra - it's easier to cut off excess than to add more.
If you don't have access to at least a budget soldering gun, do yourself a favor and get one. SOLDER your joints: scotch-locs will work fine - if you only want things to work reliably for a couple months.
Also buy NAPA glue coated heat shrink tubing - it will shrink down to a water/corrosion proof seal - the 8 inch piece of 2" for the connection at the receptacle is also a couple bucks a foot - but worth every penny!
Run the cable from the rear of the truck up under the hood. Tie into your wire harness from the bundle coming out through the firewall. Find each "feeder": left turn, right turn, parking lights, etc. Use each feeder to activate a 30 amp relay (don't use auto-zone or Pep Boys relays here - they are overrated) from NAPA. Keep all your connections in as orderly a fashion as possible, all under the hood, away from road salt, water and gravel. Your connections will last longer, and a roadside repair (or any maintenace for that matter) can be done standing next to the fender, not under the truck in the dark.
This way, each required signal at the receptacle is fed through the relay, the power is provided directly from the battery (through an inline fuse).
Wire up like this and you will never overtax your factory switches, you will always have enough amperage at the tail end, and a power problem (i.e. short, etc) will not take the whole truck down - it will simply blow its individual fuse.
To take this all one step further, you should wire your headlights through relays - use the existing power to each beam to activate the relay, feed the power to the bulbs through the relay through an inline fuse from the battery.
Basic rules:
* use inline fuses for everything
* feed each circuit through relays
* solder - don't crimp or wire-nut - your connections
* use good glue lined heat shrink tubing
* take the time and spend the few extra dollars for good quality wires and cables and plugs
* be sure to use wire sized to the needed load (and then some)
* keep circuits the right color - you will be happy for that 3 years later when you are tyring to trace something out
* don't count on the ball or 5th wheel hitch to conduct your ground - run a wire through the connector
* if you do it right, you only have to do it once
Time spent now while the weather is nice will transform trailer wiring from an annual or monthly frustration into a reliable system that will always be there when you need it.
There are some basic color schemes, and standard wiring configuarations to be found with simple web searches. The wiring diagram is printed right on most good relays. Your trailer brake adapter will always come with wiring instructions when new, can often be found on the web if you bought it used.
One last tip.
I intentionaly "miswire" my trailer connectors. On my trucks the wire normally used for running lights is connected to the trailer brakes, and vise versa. This makes my trailers un-stealable. Anyone else hooks up to one of my trailers, turns on their lights, and the trailer brakes lock up. If anyone else wants to borrow a trailer, I honestly tell them that the wiring is incompatable with their truck and so I am unable to loan it out. (I made up an adapter plug cable so I can borrow theirs)
05-14-2007, 09:15 AM
#5
Registered User
I just did trailer wiring for my rig. Only 6 running lights, 2 combo lights (brake, turn, running), and 4 brakes on the trailer. Do I have to worry about anything? I tied the running/turn/brake lights into my tail lights using a adapter from O'Reilly's. My brake controller only ties into the wire from the brake pedal to sense when I am applying the brakes, the main feed is tied directly to the battery with a 20 amp inline fuse. Then it goes directly to the 7 round plug. I want to make sure this thing doesn't quit on me and then I face a big fine.
And how do I do relays?
Jon
And how do I do relays?
Jon
Last edited by dieselJon; 05-14-2007 at 09:15 AM. Reason: More info
05-14-2007, 10:09 AM
#6
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hoppy makes a solid state relay system that works well. one hot wire to relay block then uses truck lights as signal to trigger trailer lights. on my truck for years and no problem. same as relay system mentioned above, just a little cleaner and eaiesr.
Clark
Clark
05-14-2007, 10:57 AM
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wow thanks guys I can tell this advice comes from experience and I appreciate that. I'll get to this as soon as I have time, hopefully this week!
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05-14-2007, 12:48 PM
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The Hoppy kit is a good bet, if it in fact brings the load power directly from the battery. Some do, I have a Hoppy wire adapter here that is just a couple plug adapters, and it does not - it just pulls power from the existing lighting harness.
If you want to wire your own relays, here is a website that gives the basics.
http://www.classictruckshop.com/club...h/foglites.htm
http://www.rowand.net/Shop/Tech/AllAboutRelays.htm
Radio Shack and Advance Auto (and maybe some others) sell relays whose contacts are overrated, and will fail far below the 30 amp rating - get the good ones from NAPA. Just ask for a Bosch 30 (or 40) amp relay.
This information will help wire ANYthing.
There are a lot of ways to do it right. Doing it yourself, you learn how everything works - makes it easier if you ever have to troubleshoot things.
If you want to wire your own relays, here is a website that gives the basics.
http://www.classictruckshop.com/club...h/foglites.htm
http://www.rowand.net/Shop/Tech/AllAboutRelays.htm
Radio Shack and Advance Auto (and maybe some others) sell relays whose contacts are overrated, and will fail far below the 30 amp rating - get the good ones from NAPA. Just ask for a Bosch 30 (or 40) amp relay.
This information will help wire ANYthing.
There are a lot of ways to do it right. Doing it yourself, you learn how everything works - makes it easier if you ever have to troubleshoot things.
05-14-2007, 01:59 PM
#11
Registered User
O'Reillys had it. I think I paid under 200 for it and the wiring harness.
Edit: I was told to go with the adjustable since they save the brakes alot better.
Jon
Edit: I was told to go with the adjustable since they save the brakes alot better.
Jon
Last edited by dieselJon; 05-14-2007 at 01:59 PM. Reason: More info
05-14-2007, 02:32 PM
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Hmmm. The unit (called a converter/isolator) shouldn't cost more than about $30. It's often used on vehicles that cannot simply tie into to the vehicle light wiring due to on board computers that think the additional lights represents a short in the wiring. It's basically a 4 to 3 wire converter that is externally powered. It just uses the tail, stop and turn connections as "signals" to activate the circuit without using any current from the vehicle light circuits. Look at the bottom left side of this page....
http://www.go-rv.com/coast/do/catalo...roductId=13189
or for higher power...
http://www.go-rv.com/coast/do/catalo...roductId=13163
http://www.go-rv.com/coast/do/catalo...roductId=13189
or for higher power...
http://www.go-rv.com/coast/do/catalo...roductId=13163
05-14-2007, 09:25 PM
#13
Registered User
We're Just Getting Started
Under the neck of my "Sunday-go-to-meetin' " trailer, I have a gutted house-type breaker-box, that all my trailer circuits lead in to.
I have each section of numerous lights fused seperately, before being tied into the main trailer-light-supply from the plug.
Left and right turn are also fused in this box.
All ground wires come to a main ground in a seperate junction box.
There is a bundle of wires, as big around as my arm, going in and out of this box; and, I don't even have electric brakes on this trailer.
All this may seem complicated; but, it sure makes finding a problem a whole lot simpler.
Also, should a light circuit develop a short, it will shoot the fuse to that circuit, and I don't lose the whole trailer's worth of lights.
When a fuse shoots, I know that the problem will be in that particular circuit, and I don't have to track it down.
I have each section of numerous lights fused seperately, before being tied into the main trailer-light-supply from the plug.
Left and right turn are also fused in this box.
All ground wires come to a main ground in a seperate junction box.
There is a bundle of wires, as big around as my arm, going in and out of this box; and, I don't even have electric brakes on this trailer.
All this may seem complicated; but, it sure makes finding a problem a whole lot simpler.
Also, should a light circuit develop a short, it will shoot the fuse to that circuit, and I don't lose the whole trailer's worth of lights.
When a fuse shoots, I know that the problem will be in that particular circuit, and I don't have to track it down.
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