The LM1086 is an adjustable Low DropOut (LDO) regulator with a maximum of 1.5v drop at 1.5A load. you need two external resistors to set the output voltage of this regulator.
Don't forget to add a capacitor to stablize the output voltage as you do with all other regulators, you do it right?
Adjustable range of 1.25v to 15v, to calculate the output voltage, assume you have R1 between (OUT) pin and (ADJ) pin, R2 is from (ADJ) pin to circuit GND, (check the image above), the formula would be
Vout = 1.25V * (1 + R2/R1)