most vehicles have one circuit(and one fuse) for the first 3 fan speeds and a separate circuit and fuse for the highest speed.
AnswerCHECK THE BLOWER MOTOR RESISTORThe A/C - Heater blower motor will be located on the passengers side behind the glovebox and you will have to loosen the dash on that side and pry it up very carefully.......
There might be a bad fuse causing the heater to not work. Check the fuses if they are all ok you may have a bad blower motor. when you turn the heater on and no air is blowing then it is your blower motor.
it is on the passenger side conner on the fire wall
DON'T turn it on.
check the blower motor resistor
you have a bare wire touching on your blower motor
possible rear heater blower wheel has broken center hub!
Probable failed heater core.
Defective Blower Motor Resistor Pack.
probably the heater core is plugged
There is a large amount of leaves or pine needles in the blower wheel. It most likely gets worse the higher the blower setting, the faster it spins...........
how to change heater core in 98 suburban