If it's a 3-pin voltage regulator, they're usually fixed voltage devices, with the common (ground) switched to 13/18V by the microprocessor.
For instance, I have a receiver which uses a 12V regulator for the LNB output (not an SMD type) with a 21V supply on the input pin, and the normally 12V output raised to 13V or 18V by raising the ground pin by 1V (vertical switching) or 6V (horizontal switching), switched with these voltages by an input line from the processor.
Looks like an SOT89 regulator has the centre of the three pins as the ground terminal, connected internally to the heatsink, and the output as pin 1 and input pin 3. Whether it's a 12V regulator you have, I wouldn't know.