2004 Chevy Blazer- Im adding a 7 prong adapter to my 4 way flat for a camper. I need 12v power to the rear so it will charge the camper battery while on the road. Where is the best place to pick up 12v (besides the obvious) and will I need an inline fuse?

 

So no one knows where to pick up 12v near the hitch of '04 Blazer?

 

You said not to state the obvious...

The load that will be added to any circuit that is at the back with constant 12V (if there are any) would be enough to overload that circuit. The only solution is running a 12ga or larger wire to the fuse box under the hood.

I assume you have checked to see if your truck already has the 7-pin wiring at the back tucked up into the rear-most frame cross-member..? If it does, there should also be a red wire under the hood taped up near the fuse/relay center with a ring terminal already on it for connection to the B+ post on the front of the fuse/relay center.

 

At first glance no I didnt see the wiring but my B+ terminal is wired already so I'll drop the tire I guess and get a better look. Is it common for '04 Blazers to come wired for seven pin and is it wired separate from the 4 way flat set?

 

The wire wouldn't be hooked up already if you had the 7 pin unless someone hooked it up.

The 7-pin harness includes the wires for a typical 4 pin.

 

Ahhh I see, pulled the wires and there were only six. So I was gonna run the power to the battery with an inline fuse but you mentioned directly to the fuse box?

Also, any experience with this mount for the 7 way. I have the tube hitch and see no where to place it unless I tap into the bumper. All the mounts are 90 deg.


Mounting Bracket for 7-Way Draw-Tite Accessories and Parts 18138

 

So you have six wires , what are the colors?

Here are the colors for a 2000:
Red --- Battery + (via the lug mounted wire at fuse box)
Brown --- Park Lamps
Yellow --- Left Turn/Brake
Dk Green --- Right Turn/Brake
Lt Blue --- CHMSL
Black --- Ground
Lt Green --- Backup Lamps

Most 7-pin have a pin for the trailer brakes (blue wire).
The CHMSL is not normally wired to the 7-pin.

And to top it off, not all 7-pin plugs are wired the same.

 

Two white- one larger gauge
Yellow
Green
Brown
Blue

 

So I have the 4 way to 7 way adapter on just need to power it. If I connect to the battery will that charge the camper battery as well or should it go to the under hood fuse box as previously stated, and if so where? I would be disconnect the plug when not driving. I need to get this Pup on the road And just curious, what is the light blue aux stoplamp wire used for on my six wire harness? Adding Extra lights in the back?

Also.. the rear defroster that I never use, would that be a an option for 12v? Plus I could turn it on and off.

 

Aux Stoplamp is the Center high mounted stop lamp (CHMSL) only on with the brakes. It is usually fused for 10 amps.

Check the wires at the back with a meter and confirm the function of each, one of them should be the constant 12v from the red lug wire on the fuse box. Not sure why none of your wires at the back are not red, try the largest wires first. Make sure you can read 12v at the front lug then look for it at the back with the meter.