1997 Chevy Tahoe Heater Blower Issue

Hello - My Tahoe blower motor only runs when the blower motor switch is on high. I have replaced the switch, relay (under the dash) and tried a new blower motor. According to my volt meter, no voltage is coming to the blower motor other than when the switch is on high. What else could be causing no power to get to the blower motor when the switch is in the lower settings? All other switches, etc seem to be working normally.

Thank you,
Neal