This is common problem,faced on many other car models too.
It could be the switch, but it's usually the resistor. Remove the glove box and unscrew the resistor from the top of the blower housing. Pull the resistor out and inspect for heat damage.Resistor is the blower motor fan speed controller,except high mode.So when blower motor resistor fail's,high mode works,but other modes don't function.
This basic details will help.Thanks.
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