Heater only works on the high setting of 4.

What is your question?

It was not the blower resistor since putting a new one in still caused my heater to work on only high setting of 4 & not on settings 1, 2 & 3. Works the same using a/c.

What makes this problem better or worse?

Nothing so far.

How long has your 2013 Dodge Avenger had this problem?

A couple of years