AC blower when turned to 1-3 will blow great but on 4 and 5 it blows nothing. on 2004 Isuzu Ascender

All 5 levels worked until a few months ago. 4 went out and 5 worked ,now 4 and 5 don't work....hear electronic hmmming in background.

Asked by for the 2004 Isuzu Ascender
Blower motor regulator
Thank you! I'll check it out