Climate control questions ...

[78 450sled]

I have a 78 450 Sl and when I bought it the climate control servo was out of the car and broken. I recently purchased what appears to be a good one. It looks fine inside and out. I have installed it but I still get no air except for defrost which I understand is normal. When I turn the car off I can hear the motor inside the servo working. If I look into the center vents I can see them opening but the fan will not blow when I push any of the AC buttons. I have read about an amp behind the glove box but I'm not sure what to look for once I find it. . When I turn on the AC switch the compressor does not work either. It seems to have vacuum to the unit but even when the engine is at 3000 rpm it the fan will still not come on.

ANY ideas would be appreciated.