Heater Blower Fan Speed

[Brother Bill]

I installed a new blower fan switch in my 1986 4000 CS Quattro today
because I was only getting the #4 speed (highest) for my heat.  Well,
with the new switch installed I get the same thing, only the highest
setting works.  Does anyone know why?  I'm told there might be a ballast
resistor near the fan motor but I'm not sure.  If I do need a new
ballast resistor does anyone know what the part number is?  My car year
and model is listed above.  Thanks for any info anyone might have.
Bill