I just bought a 19' travel trailer and it has a 7 pin round plug. So I needed to make an adapter to go from the factory 7 pin blade to a 7 pin round. I had the local hitch install place make the adapter. I plugged it into the truck and trailer and here is what I got. The left turn light stays on all the time (not blinking). When I turn the right blinker on, all the marker lights and the right turn light flashes. When I push on the brake pedal, no brake lights come on. Obviously the wiring is mixed up. I found the wiring diagram for both 7 round and blade on the internet but here is my problem. The diagram for the 7 round does not show where to plug in the 12V+ or electric brakes. Can someone look at this website and tell me which wires go where? Scroll down to the bottom of the page and you will see both the 7 blade & 7 round diagrams. Thanks in advance. Mark http://www.crbrophy.com/elec.html

 

I used to work in a travel trailer dealership and did all the hitch and wiring. I've never heard of a trailer wired with a 7 pin round plug. All I have ever seen had the 7 pin blade plugs. I would use a tester and check the trailer end. It sounds to me like someone wired in a new plug on the trailer. The way the 7 way round is set up it splits the turn signals and stop lights as well as running lights and tail lights. I doubt if that plug will work with what you have.

Barry

 

http://www.etrailer.com/faq/wiring.asp Check this site out for wiring diagrams. It has helped a lot of guys. Goodluck,,Rick

 

It may be worth it to purchase a matching pair of connectors (or one end to match the other) and re-wire both of them so that you are sure they are correct. If you are towing other trailers, that may not be the best way to go, but it may be the simplest solution to your troubles. (also makes the connection look much cleaner)

 

First off...thanks for the replies. I hate electrical work. Do you think I can change the trailer plug from a 7 pin round to a 7 pin blade to match my truck?

 

Its not rocket science most plugs are even color coded
Good Luck

 

The ones on my truck are color coded, in fact, i even have a pollak set sitting right here that is EXTREMELY easy to hook up and use.

 

I'll dig into it soon. I did take a look at the trailer plug and I see there is a red wire. My truck's plug doesn't have a red wire. I just don't want to fry something by getting wires crossed.

 

if your trailer is factory wired you have no real worries and all the wires may not be there thats ok.

 

I'd definitely wire up the trailer to a blade plug in. It's not hard, just make sure you don't pull one of my stunts and have the sheet upside down and wire the plug upside down It doesn't work very well that way...

 

Your best bet is to get rid of that 7 pin round plug on your trailer.

When you disconnect all the wires and remove the round plug, you'll have to ID each wire's function.

Start off by IDing your trailer ground wire- it's usually screwed to the trailer tongue nearby the hitch. Make up a jumper wire from trailer ground to pin #1 on your truck. Use small alligator clips on both ends of the jumper wire.

Then make up a 2nd jumper wire from truck pin #4 (12v+) as a test lead.
Hold it to each wire on the trailer in turn to ID what lite comes on.

The wire(s) that lite up you taillites and marker lites would go into pin #3 of your new plug.

The wire that makes the left stoplight glow bright goes into pin #5 on the new plug

Right side light glows bright, pin #6

So, now you've found the right wires for pins 1,3,5,6

You'll hear your brakes set up when you touch the test lead to the brake wire- that goes into pin#2

Pin #7 is not used, except maybe for backup lights on the trailer

That leaves the only wire left from the trailer as the +12v feed, which goes into pin #4

Just take it step by step.
The only thing you may fry is the trailer fuse in the truck- and there's extras on the panel cover.

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Mark
Just get the ground in the right place.....that one will blow fuses...the rest is easy.

 

And make sure you're not talking to someone else about wiring up the plug correctly while you're working....because you'll surely find when you're done that the left blinker on the truck flashes the right blinker on the trailer. Don't ask me how I know....