Alright so I haven't found a thread on this, the other day I was messing with the knob that turns the air pressure up and down for ac/heat well the other day full blast (number 4) decided to stop working and only 1-3 work now irk why it happend but it just stopped working anyone have this issue?

 

Possibly blower motor or the relay for it. That would be the first place I checked.

 

im having the same problem. pull and check your switch. it works very very intermittently. =-) luck