Quote Originally Posted by Dubious Drewski
That seems pretty straightforward to me...
Indeed it is. That variable power knob should lower the flash output regardless of how the modeling light is set.

Aside from something being busted, the only thing I can think of is that the flash is already fully charged when you turn down the setting. In that case, the full powered flash would still fire.

So what you need to do when you lower the setting is first discharge the flash (using the test button). Then it should recharge at the lower power.

If it is indeed not working right, and you don't have the resources to get it fixed, you can still lower the output by using modifying material in front of the flash. Scrims are dark stretched fabric that block some of the light. Sort of a neutral density filter for light.

They're kind of pricey from a photo or grip store, but like much studio gear, you can probably make your own cheaply. You might try fiberglass screening material...