I believe that it is very touchy and you have to do it very gently so that the off lines up with the one on the knob exactly and if your's is as smooth as mine it is very hard to find that line with out going over or under.
My 2001 Chevy Blazer was blowing cold air when I had the heat on. My husband flushed the line to the heater core and a bunch of junk came out and now my heat works great. My 2001 Chevy Blazer was blowing cold air when I had the heat on. My husband flushed the line to the heater core and a bunch of junk came out and now my heat works great.
Check the engine thermostat. Its probably stuck open.
The temp blend door actuator is probably at fault.
A bad engine temp sensor can do that.
Check the 96 Blazer for any vacuum leaks in the system. A vacuum leak can cause the air flow to only come out of the heat vent.
It is located under the AC and Heat instrument panel
Is it blowing cold air only or not blowing any air at all.
Only if it is allowing Fluid to escape. Does the radiator and heater core have enough fluid to circulate. If not you will not have heat.
Drain the blazer radiator. Refill with water. Open the heat on high, start the engine for a few minutes. Drain the system again Repeat this several times to get all of the old coolant out.
No heat, engine doesn't cool down properly, after the engine warms up to a point where the thermostat should open up, the coolant lines don't have a fairly uniform temperature throughout.
If your windows fog up you thermostat may not register because you heater coil may be broken.
Heater Airbound? Heater control cable not working? Heater core plugged?