The heater blower motor either does not work or works weaker?

Heater blower motor either does not work or works weaker than what speed is set, until I make a right turn. When in a right turn the blower speed appears to increase to the actual setting speed. Once the wheel straightens out, the speed returns to either no blowing or less than speed set. Vehicle has to be moving. If parked, and I turn the wheel right, nothing changes. Turning left makes no difference.