Chevrolet Repair: blower, amp fuses, resistor pack

Question
blower motor only runs on high speed not low and the two medium speeds, I checked both 20 amp fuses one under the dash and under the hood and both checked fine?

Answer
Hi George,
Hmmm...so what are we driving? Car, truck,...?
The problem is the blower resistor pack, which is located somewhere in the blower housing, so the resistors can be cooled by the airflow.
On a pickup, like a Silverado, that is usually behind the glove compartment.
On an S10, there is a section of the blower housing under the hood that actually needs to be cut out to access the resistors.
In a car, it could be under the hood, or under the dash.
But whatever you have, that is almost 100% the problem.

Van