Check for a vacuum leak -sounds like it is starving for vacuum and reverts to the default position
If central air conditioner turns on but is not blowing through the vents, check the filter. If it is dirty, change it. Change the thermostat into cool, this will defrost the air conditioner.
When there is a problem in the vent system it defaults to defrost setting. Check the doors & vac supply
you have a vac. leake or the oneway check valve is not working.....
No power, no air! Simple
If your air conditioner is running outside by not blowing cold air inside through your vent, your indoor coil is frozen. You will need to turn everything off and allow the unit to thaw out.
The vacuum supply line from the engine is disconnected or broken. When the vacuum supply is cut off the system defaults to the defrost mode.
2003 crown vic air conditioning vent dont blow
The 2003 Chevrolet trailblazer air conditioning line can be found on the air conditioning compressor. The line goes from the compressor to the firewall. The line will go through the firewall to the air conditioner core.
this one is easy your switch the controls the vents is not working there is a flap the closes the defrost vents so that it goes through the other vents or there is a vacumn line that is controlled by the switch, and its leaking. The vacumn line is usually on the engine side of the firewall. It is a very small plastic tube comming out of the middle of the firewall at the top and it connects to a junction with other vacumn lines. See if any of them are disconnected.
Check your blend door for proper operatin. Check your ac gas level. make sure your condenser and orice tubes are not stopped up.
when it happened to mine, it was because the arm behind the dash that controls the internal vent doors slipped off
Check under the hood for a disconnected or damaged vacuum line. The controls are vacuum operated and if the vacuum supply is cut off the system defaults to defroster only.