Welcome to the 'bolt hillbillytim;
A voltage drop resistor doesn't work until it's actually in the circuit with current going thru it. If you just hook 12 volts to one end and look at the other end (not connected to anything) it will still read 12 volts. To see if it's the right value for the circuit it's in: connect it in series with whatever load it is going to power, (turn the load "on", i.e. heater motor, radio, etc.) then read the voltage at the output of the resistor to ground. Should be somewhere in the 6 volt range.
