I just bought this 96 Blazer for $4oo.oo bucks, put a 98 engine for $650.00 in it and we're on the road. But we have a few problems. The condencer was bad, replaced, pumped down the system, recharged, cool air. The blower control switch only works on the top two speeds. We put in a used switch but, still got the same results. We also have a vacume leak behind the dash, air only comes from defrost and floor vents. we'll fix that when we replace the heater core. Do you really have to pull the entire dash and drop the steering wheel to do that. I replaced the core in my 96 S-10 pickup many years ago and I don't recall having to do all that. Any help on that switch thing would be appreciated.
I would suggest checking the blower motor resistor, mounted on the heater box in the engine compartment.
Often a wire will burn out in one of the resistor coils and you will lose one or more of your fan speeds