1991 gmc blower motor speed

[red1]

my 91 has the 3 speed ac/heat blower motor. only one speed works, high. I have not had this problem before what part should I be looking for? relay or resistor ?

 

[skylark]

The resistor. It is behind the glove box in the top of the heater box.

 

[red1]

I thought that's what it might be with the fact I lost low then medium and now high is acting up