Can somebody help me understand these.....like the timeline?

Okay the four pin flat has been around forever...I got that. Ground running lights brakes and turn signals.
What is the five pin flat? If it is more modern then why does my 2015 F350 have the four pin flat? What does the five pin flat do?
Okay then we have a six round that I presume was around before the seven pin round?

On the seven round does your trailer have back up lights?

 

There is a good chart on this page that describes what features every connector includes.

https://www.etrailer.com/faq-wiring.aspx

 

Thank you that is very helpful
Looks like there are many more types of connecters than I thought.

 

its a World economy ..

just like the various laws, for turn signals... cars/trucks/trailers/motorcycles/etc.

or mandatory running (driving) lights.. Canada must have them...

USA not... for cars/trucks... IS for motorcycles with headlight On if engine is running.
.
.

 

The 5 pin flat includes a pin for trailer brake lock out solenoid. For example, a boat trailer will often have surge brakes that engage when you go to back up, so an electrical solenoid may be incorporated to prevent the master cylinder from being engaged. Otherwise you'll have to get out and insert a lock out pin or similar before backing.
The six pin round is typically used on trailers that do not have a battery/charger circuit, but do have electric brakes - such as horse trailers.
The seven pin rounds are used on trailers that do have on board battery/charger, such as travel trailers, etc.
I'd say the appearance of each of those connectors is in that order as well, since they are developed to support the growing needs of whatever is being pulled.

 

That is interesting....I thought the 5 pin was for when the brake lights are separate from the turn signals.

 

Well, they are. The brake lights are usually brown wire, left turn yellow, right turn green. The back up wire is used to activate the surge brake lock out solenoid.


The four pin flat also will support brake, left turn, and right turn, using the same color wires as the five pin.

 

In a nutshell:
4 flat. Standard for small trailers, and boats. Most common
5 flat. Kinda an oddball, never made it's place or mark. Very rare to see.
6 round. Heavy duty metal plug. Common on farm and construction equipment and other heavy duty harsh environment applications.
7 blade round. Standard RV plug. Also seen on gooseneck flatbeds.
7 pin round. This is a semi truck and trailer plug. Only mentioning so you don't grab one by mistake at a truck stop.

By far the two most common and most used are the 4 flat and 7 round (blade). Just about anything you buy will have one of the two. Most vehicle towing packages come with a 4/7 combo.

 

For the past several years pretty much all livestock and horse trailers also use the 7 blade round, as most come with a rechargeable breakaway system. Many older trailers (and trucks) are being converted as well, in the interest of compatibility.

 

Very true. A lot of heavy farm equipment that is towed on roads or that has the need for 12v power uses the heavy duty metal six round. Just because it's do tough. I do agree that it's being phased out and replaced by the 7 round.

 

I have a lot of trouble with the plastic 7 blade round connectors breaking, thinking about adding a 7 pin round semi type plug to my truck beside the 7 blade round plug, then I'll rewire my trailers the semi plug, my ag equipment already uses the semi type plugs

 

I don't know who's plugs you have been buying but my truck plug is from 2002, factory Dodge, and my car trailer has been on it longer than that.


The plugs I think are Pollak.
Dave ----

 

Around here everyone sells Hopkins.
I spent 30 years using the heavier semi style plugs, their much more robust than the cheap plastic RV plugs.

 

I have had issues on my semi with that plug too. Not breaking but not making good connection, lights flashing on trailer going down the road.


Link to E-trailer plugs. I see Pollak also makes a metal one if you want to go that way https://www.etrailer.com/s.aspx?qry=...tor-pc-7_Blade
I Have also used the metal ones and never had any issues either but all I have used is Pollak.
Dave ----

 

5-pin flat plugs certainly do have their place; on boat trailers with surge brakes, where the additional wire (blue, I think?) activates a brake release mechanism in the trailer coupler that prevents the trailer's brakes from being applied while backing up.