So I need to be able to wire up to a heavy duty trailer with the 7 pin RV blade ( I think that's what it is) coming from the trailer to the blazer.

On my blazer, I have a Uhaul hitch, and the plug on my hitch is labeled UHaul...so I don't know if it's special or what...but it's 8 pin.
Two flat 4s on top of each other:


Now I've hooked my jetski trailer up all the time to this sucker, the jetski trailer is only a flat 4 pin, and the trailer has no brakes, just turn signal and brake lights. All of that works great when I put the 4 into the bottom of my 8 pin thing.

But the trailer I need to tow with the 7 pin needs brakes, and thus I need an adapter. I got this adapter at autozone the other week when I was towing it, and needed brakes. I'm not sure if they actually worked though..and I know for a fact the turn signals never worked (whether it was the trailer or my plug, I don't know!)
The adapter has these ends:

And these two random wires (purple and white).


And the plug set that mounts on the hitch end of things is this:


Basically, I have no idea whats supposed to hook to what. I had to cut the 4 pin side of the adapter (it had a rubber sheathing around the pins which made it not fit into my UHaul thing) and that's what I thought got the trailer brakes working but I don't know!

Help please!! Can I just cut off the 8 pin uhaul thing and wire in the adapter I bought, or will it work fine just plugging in...and where do the purple/white wires go....and is this even the right adapter?!?!

 

I went to a hitch installation shop (Hitchco) and they have a showroom full of adapters and some knowledgable people there.
I bought a 4 pin adapter that just tees into the factory wiring on my truck. No cutting or messing around for $20.
You should be able to get a connector that will go from a flat pin to the round style also.

My boat trailer has mechanical surge brakes so my 4 pin connector is fine.

[IMG]local://upfiles/2910/72E81FEF9E644C63975843E6CD08ED38.jpg[/IMG]

 

Well..I don't think I can return this adapter I've got cause I had to cut the rubber sheathing off the 4 pin side, so is there anyway I can make this adapter work? Should I just cut off the 8 pin UHaul monstrosity and splice in this adapter? Or can I splice in regardless and keep the 8 pin (either method is fine). I just need to have the 7 pin plug wired in, and a 4 pin for the jetski trailer...but I would really like to avoid hunting down and finding a new adapter piece for another $20!

 

Check your owners manual! It has the wiring information for the pre-wired trailer wiring. If you follow the 4 pin wire back, it should go into a larger bundle of wires where there should be additional wires that will connect to the 7 pin harness.

 

Ahhhh I didn't even think to look at the manual..I got too caught up in not having directions for the adapter!

So it would be easiest just to cut off the 8 pin thing and wire up this new guy if I just follow the wires back to the source!

 

Check to make sure that you have all of the wiring, and then yeah, it would be much easier to just cut off what is there and wire in the new one. If you need the 4 pin connection, its there on the side. If you need two of them, you can always get a 7 pin to 4 pin adapter to use along side the other 4 pin.

 

If the trailer you are going to tow has electric brakes you are not only going to need a 7 pin adapter, you are also going to need a brake controller. The controller regulates the current to the trailer brakes so they don't go full-on every time you hit the pedal.

On the 7 pin connector you will probably only use5 of them. Follow the wiring diagram in the link. The auxilliary/back-up is not usually used.

Trailer Wiring Diagram For 4 way, 6 way and 7 way circuits

Brake controllers are not exactly cheap but they are absolutely necessary to use trailer brakes. Here is a link to one site to give you an idea about the different types.

Brake Controller

Cut off your two 4 pin connectors and follow the wires to the harness from your truck. This harness will contain most of the wires you need except for a 12vDC power which you will only need if the trailer has batteries to charge, such as an RV. Just remember that if you connect the light blue wire without the controller the trailer brakes will go full-on as soon as you hit the brakes.

 

That's the link I was just looking for Alan! I know I've either linked to it before or just linked to the picture of the trailer before, but couldn't find the thread.

 

hello everyone. I am a new member and have found this thread quite usefull, but my problem is a little different.
I have an 02 blazer with no heavy duty wiring package(no tow package).
i have recently bought a tent trailer (no brakes)and would like to be able to charge the trailer battery while towing. I have had a hitch and 4 flat wiring connecter instaled, so there is no wire to provide 12vdc. what would be the best way to run 12v power to this battery and will the electrical system handle the power draw with out being upgraded with a tow package?
thanks for any help you can give me with this.

 

Shouldn't be a problem. I would just get some 'primary wire' (two wires in a protective covering) and wire that up fused and switched to the battery. Then run it back to the rear bumper and finish it off with a two pin connector similar to the flat 4 pin connector for the trailer lights. Use the other half of the 2 pin connector and wire it up to the battery. Your charging system should be more than enough to keep the battery on the camper charged up, but I would not leave it connected while the engine is off for fear of draining the truck battery if you are using the camper lights.

Now, by switched, I mean to install a switch or relay and switch on the wire running to the back so that you can control when it is on and when it is off.