7 pin connector

[Andymon]

So I replaced the 5 pin connector on my 99 F250 with the OEM 7 pin that was complete with wires and end connector. Connected it to the TT and only the left rear blinker on the TT works. I'm guessing that obviously the wiring is mixed up on the trailer. Checked the bulbs and they are all ok.

[davidjsimons]

Check your ground to make sure it is sufficient.


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[Andymon]

Originally Posted by davidjsimons

Check your ground to make sure it is sufficient.


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The ground coming from the batteries on the trailer?

[davidjsimons]

The ground on the wiring harness for your lights. Also, hook the trailer to the truck while testing. The ball grounds to the hitch as well. You can also take a test light and hook it to the positive side of the RV battery and check the light plug on the trailer one prong at a time. This will put current to each light and help you to decide if the problem is in the truck or trailer. Then take the test light, ground it to the truck, and check the plug on the truck.


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[raytronx]

Just finished trouble shooting a problem with my lights, found these diagrams helpful. Colors may not be the same but gives you an overview.

Ray

[JRTJH]

I would think the trailer is NOT the problem. The truck is what you just worked on, the trailer was working properly when you towed with the previous truck, so the trailer (unless you've been moving wires around) has "known good wiring"

Go over the truck's wiring very carefully, somewhere you may well have a miswired connection or two. Do a step by step check using the diagram shown above. REMEMBER how you're looking at the pins, don't go in the reverse direction thinking left is right. Once you know the truck is wired correctly, then, as David said, the ball/coupler provides a common ground for the trailer/truck. I'd hitch the trailer, install the WD bars, plug in the 7 pin connector and see what works.

[Andymon]

Originally Posted by JRTJH

I would think the trailer is NOT the problem. The truck is what you just worked on, the trailer was working properly when you towed with the previous truck, so the trailer (unless you've been moving wires around) has "known good wiring"

Go over the truck's wiring very carefully, somewhere you may well have a miswired connection or two. Do a step by step check using the diagram shown above. REMEMBER how you're looking at the pins, don't go in the reverse direction thinking left is right. Once you know the truck is wired correctly, then, as David said, the ball/coupler provides a common ground for the trailer/truck. I'd hitch the trailer, install the WD bars, plug in the 7 pin connector and see what works.

JRTJH, We've never towed the trailer yet. Everything on the trailer is original so I don't think the problem is with the trailer either. Will check more on the truck.

[SteveC7010]

One important point here. I think it's problematic to rely on the ground between TV and TT at the ball and coupler. Many of us lube our couplers and that creates a barrier to a decent electrical connection. At best, the ground will be intermittent. On a fifth wheeler, it would be very, very unreliable from the get-go.

You are far better off to first verify a good ground on the TV at the 7 pin and a good ground on the TT at the pigtail. Together they are an appropriate electrical connection between the two vehicles. I would connect the pigtail to the truck without dropping the coupler on the ball. If you don't have a good ground circuit through the 7 pin between the truck's frame to the trailer's frame, you might well never locate any other issue that may be present.

On many RV's, the ground from the pigtail is connected to the frame with a standard grounding lug. If that screw on the wire comes loose or gets corroded, your ground can go away all together. I have not located the lug on my Cougar yet, and I may just go into the pigtail box up behind the pin box and add my own secure ground. My Sunline had a grounding lug like this one. It was attached to the frame just where the A-frame connects to the regular frame.


Since there was a conversion on the TV from 5 pin to 7 pin, that would be where I'd concentrate my troubleshooting. If you can get one, they make a little tester that will plug into the 7 pin on your truck and almost instantly verify stop, tail, and both turn signals. It also verifies ground, but I would still use a multimeter to check ground, hot, and reverse.

Brake controllers are more sophisticated these days and can sense when connected to the trailer. A meter may not duplicate that electrical condition by itself. Check out everything else and then verify braking current with the TV and TT hooked up.

Another common problem when rewiring is poor connections inside the new 7 pin. They are screw terminals. The wire should be clean shiny copper. If it's dull green, cut that off and strip back another 1/4" or so. Twist the strands neatly with no strays outside the terminal. Insert the wire between the two plates of the terminal all the way so the the insulation is just touching at the end, but no insulation between the plates. Tighten the screw securely and move to the next.

I live in the northeast US where they use a lot of road salt during the winter. Corrosion of electrical connections is a common issue here. To beat it, I use dielectric grease on all screw terminal and crimp connections that might be reached by moisture and/or road salt. All wiring is encased in loom and taped up with quality vinyl electrical tape. Wire to wire connections are either high grade crimp with adhesive heat shrink or twist and solder (rosin core only) with adhesive heat shrink.

[rhagfo]

Originally Posted by davidjsimons

The ground on the wiring harness for your lights. Also, hook the trailer to the truck while testing. The ball grounds to the hitch as well. You can also take a test light and hook it to the positive side of the RV battery and check the light plug on the trailer one prong at a time. This will put current to each light and help you to decide if the problem is in the truck or trailer. Then take the test light, ground it to the truck, and check the plug on the truck.


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Best to test with the trailer DISCONNECTED from the TV! This test the ground connection on the plug, this is the ONLY way I test mine, I DON"T count on the hitch to make the ground connection. The hitch is an inconsistent ground, and I will not count on it for anything!
Do you want to trust your brakes to an inconsistent ground?????

[Andymon]

Originally Posted by raytronx

Just finished trouble shooting a problem with my lights, found these diagrams helpful. Colors may not be the same but gives you an overview.

Ray

I just took off the 7 pin connector and see that instead of a purple wire in the middle, there is a red wire. All the other wires are correct. I also saw tht I just might have not got two part plug pushed together tight enough. Hopefully that's the problem. I'll check again this weekend. thanks!!

[SteveC7010]

Originally Posted by Andymon

I just took off the 7 pin connector and see that instead of a purple wire in the middle, there is a red wire. All the other wires are correct. I also saw tht I just might have not got two part plug pushed together tight enough. Hopefully that's the problem. I'll check again this weekend. thanks!!

If the 7 pin came with wires attached, the red wire may not be a problem. What you'll need to do is to determine what the red wire (center pin) actually does. You've determined that all the colors except the center pin are correct.

In my previous post, I recommended that you verify what each pin in the truck's 7 pin does. Obviously, the function has to match the diagram and pic that Ray provided for you. Just matching the colors to the pins is only the first step. Use a multimeter to check each pin for correct function.

First, set the meter to Resistance (10K is fine), and touch the two probes together. The meter should read 0 ohms. Then test Pin 1 to the chassis or fender or some reliable ground of the truck. You should also get a reading of 0 ohm.

Second, set the meter to 25 or 50 volts DC. Then turn on your parking lights and place the black probe on Pin 1 (ground) and the red probe on Pin 3 (tail lights). You should get a reading of 13 volts or so. Less than 10vdc is a problem.

Third, set the ignition key so that the turn signals will work. (Vehicle does not have to be running.) Meter still on 25 or 50 VDC. Black probe on Pin 1 again. Then test Pin 5 with the left turn signal on and Pin 6 with the right turn signal on. The meter should jump from zero to 12vdc and back to zero with the flashing of the turn signals. Also have someone tap the brakes while you are on pins 5 and 6 to make sure that works, too.

Fourth, we're going to check for voltage on Pin 4. Some tow vehicles require the vehicle to be running to enable the charge line. Others just require at least Accessory. Others still are hot all the time. You'll have to sort that out. But again, 25 to 50 vdc, black probe on Pin 1 and the red probe in Pin 4. You should get 12vdc or a bit more.

Fifth, trailer brakes. Some of the newer controllers require the trailer to be hooked up. If yours does, skip this step for now. You can test the brakes when everything else is good to go by hooking up and applying the brakes. If it doesn't, have someone step on the brakes while you hold black to Pin 1 and red to Pin 2. Again, looking for 12vdc or so.

Last, check the center Pin for reverse. You'll have to set the gear shift in reverse to do this with the key on. If you have a trusted partner, the car can be running when you do this. If not, just block the tires so the vehicle doesn't roll, turn the ignition on, and set the gears shift in reverse. Black probe to ground and red probe to center Pin 7. 12vdc or a bit more is your goal. Put the vehicle in park and test the center pin again. It should be 0 vdc.

Those are the steps to test out your 7 pin on the tow vehicle.

[Andymon]

Thanks Steve! Off to get a multi meter after work.

[SteveC7010]

Originally Posted by Andymon

Thanks Steve! Off to get a multi meter after work.

Andy, I hit submit before I was finished. I just finished it up and resubmitted so all the steps are there now.

You don't need a very expensive multimeter. It needs to check resistance, and be able to test DC voltage up to 25 or 50 volts and AC voltage up to 240 VAC. Anything else is gravy. Digital display is nice, but again not needed. The old trusty needle meter works fine.

My meter is about 10 years old and I got it at Radio Shack for less than $20. You can find them in the electrical tools section of any hardware store or home improvement center as well as Radio Shack. It should come with a little manual so you can learn how to use the basic functions.

Once you have one, you'll find that you'll use more often than you think. If you don't have a plug-in volt meter, the multimeter is great for testing voltage at the campground power post before you plug in the shore line.

And, as you're beginning to see, it's indispensable when it comes to trouble shooting 12vdc stuff in autos and travel trailers.

[Andymon]

Originally Posted by SteveC7010

Andy, I hit submit before I was finished. I just finished it up and resubmitted so all the steps are there now.

Got it and all printed. Thank you very much!

[Andymon]

Well, check the 7 pin out yesterday and the only pin that has anything going to it is the left turn signal. Everything else...nada. Will have the shop take care of it tomorrow.