Have to Fiddle with Heater Controls to Get Them to Work

[djzero]

Hi all, I have these heater controls in my 2002 GT:



Whether it's setting it at hot or setting it at cold, I always have to fiddle with it, moving the levers up and down several times and then leaving it where I actually want it before the setting will actually take effect and actually blow out the temperature I want it to. Does anyone know why this happens and what I can do to fix it?

Thanks in advance

[dsmuts]

maybe a vacuum leak.