Check the fuse block for the fuse rating first, before installing a higher rated fuse, by doing so, you will avoid parlaying the problem to the blower motor or the heater resistor/heater element. Also, check the heater wiring harness to ensure there are no bare wires.
The Deluxe heater (3-speed) set-up, utilizes the same blower motor as the Thrift-Air heater (2-speed) set-up and the fan speed is controlled by a variable speed/variable resistance switch in the dash control assembly on the Deluxe heater. Have you checked the heater switch in the back of the Deluxe heater dash bezel? You may have an issue with this switch and considering the cost of a new switch, I would check here next.
I hope this information is helpful in solving your heater issue.
