blowing cold air

2001 blazer blowing cold air when turn to heat any suggestions

2001 blazer blowing cold air when turn to heat any suggestions

Automatic or manual controls.
Any check engine lights or heater control lights on?

Coolant level?
Engine up to temp. ?
Have you checked vaccum lines and hoses.
Mileage and any service work done on engine or AC and heater system?

Had the same thing on my '96 Jimmie, discovered former owner had mixed green and orange anti-freeze, temp gauge looked fine but the mixed coolant had gel'd up enough to clog the heater core. Flushed heater core, it worked good for about a week then went cold again, flushed heater core again and now the heater works well enough to run ya outta there.