Heater problem

I have a 99 blazer.  My heater stopped working today and I was wondering if anyone could help me figure out why.   For a couple months 1-3 would work but not 4 and now today i get no air on any setting.  Do you think ints the motor or maybe the relay?
 
Thanks
 

ok so I replaced one of the hvac fuses and now i get air on 4 but 1-3 still wont work.  What do you guys think? 

Sounds like the blower motor resistor pack has failed.

quote:

In the low position, voltage passes through all 3 resistors in the blower motor resistor through the blower motor relay and to the blower motor.

In MEDIUM 1, voltage passes through 2 resistors.

In MEDIUM 2, voltage goes through 1 resistor.

The HIGH position supplies trigger voltage to the blower motor relay. This condition energizes the blower motor relay and supplies full battery voltage to the blower motor through the HVAC fuse in the underhood fuse block. Ground is provided at G117.

If you have A/C, the blower motor resistor will be located under the outer cover as shown in the image below:

You will have to cut along the dashed lines in the picture above to access it.