Fan Blows went switched off

[OssaMAR]

I just got a 1977 C20, when I turn on the ignition the blower fan runs even though the switch is in the off position.

Any ideas why this is happening?

 

[1987 GMC Jimmy]

Perhaps this.

http://www.gmsquarebody.com/threads/heater-fan-always-on.6117/

 

[Obwonkonobe]

Its normal, my 78 does it too. I didn't know why until I went through the wiring, its just set up so it always runs really slowly to keep some air circulation