72 A/c

[big dump]

So I got the top on the '72 this week and drove it around for the first time this summer (had the top off for painting and freshening up). BTW, summer here in AZ is hot in case you didn't know. Up until last night the air was working fine, but last night with the blower on high, it cut out on me. I can still turn it on the low setting, but when I switch it all the way down to hi, it doesn't blow. Where should I start? Do you think it's the switch? Or the blower motor? I hate to start throwing parts at it, any suggestions for trouble shooting are appreciated. Thanks.