Call whoever installed the 7 pin and ask if they included a charge wire.  I found that it is not standard and you must request it.  You can also purchase a 7 pin tester and I believe it will identify the presence of a charge wire, but don't quote me!

Mickey you need one of these.  It will identify the presence of a charge line.  The charge wire runs from your tow vehicle battery to your tow vehicle 7 pin plug.  It can be run outside or inside the tow vehicle and is best to avoid any contact with a hot exhaust system:)

CURT 58270 12V LED Connector Tester

(sorry, I could not post the picture.)

mandt said:

So is this beyond the utility of the 7 pin connector.? Is it just a loose wire going from the car battery to the tab battery. What kind of connector is needed? Sorry for the barrage of questions!

It goes from the battery to the 7-pin with an inline fuse, and should also run through a switched circuit so that it doesn't pull from the vehicle battery with the ignition off.

SAM said:

Carol,
How would you check if you have your charge line on a switched circuit?

I'm not Carol, but if you have a multi-meter or volt/ohm meter, you can check for voltage inside your 7-pin connector when your tow vehicle is not running. If no voltage, then your vehicle has a switched circuit that turns off any auxiliary power when the vehicle ignition is turned off. My Toyota Tacoma has a built-in switched circuit on all accessories. 

@SAM, my Toyota Tacoma has a factory tow package. The first thing I checked was if I had power at the 7 pin recepticle on the truck. No power when the ignition is off, but it is there when the ignition is on. My Tacoma charges my T@B's batteries while I'm driving. 

Is yours a factory tow package package or after market? Factory--it should be off when the ignition is off. After market--check it. 

Yes, the tester will verify power. Check it. 

mandt, the charge wire from the vehicle battery to the 7-pin is usually (should be) a heavy gauge, ie #8 or #10, and can (should) be run through an isolation relay which separates the Tab from the tow vehicle's electric system when the tow vehicle isn't running/charging. The isolation relay prevents draining your vehicle's battery.

From what I understand, some installed charge lines are not heavy gauge, unless you specify that you want it. The Tab needs it, due to the heavy draw of the three-way fridge when it's running on 12v.