1983 blazer heater blowing cold air

SOURCE: '98 Chevy S-10 Pickup heater blowing cold air

the temp door is located in a box behind the glovebox, the actuator is either under or above the box. if you remove the glove box you should be able to see it.

SOURCE: 2001 malibu-heater is blowing cold air

sounds like you have a bad temperature sensor in dash or the cable has eitehr broken or come off the heater switch under the dash!!

SOURCE: 2004 Chevy Silverado Heater blows cool air

Check blend door actuator for operation

SOURCE: 1998 Blazer A/C blows hot air...the heater works

This could be the problem "it's full of freon cause it wouldn't take anymore"
A/Cs are not filled until they can't any more.

Here is what you should have in it.
The refrigerant used should be R-134a
The total amount should be 32oz
The type of oil in the A/C should be Pag-150
The amount of Pag-150 should be 8oz

More than 32oz of R134a is overcharged.

You should also check to make sure the compressor is engaging.
If not,It could be Overcharge,bad compressor,Bad pressure switch,or a few other things.

I hope this has given you ample info.

Please take time to rate this fixya.

SOURCE: 1996 chevy blazer my air on heater will not blow

the idea of the switch is run on vacuum and is not making contact with the switch it self either worn contacts in the switch itself **** as an obstruction as well or the vent door is stuck in just that position either behind the glove box or the ash tray are the vacuum lines one of them may be pinched off or the door needs a bit of help until you can free it up