the ducts can not be hooked up for the vents to work
The most likely cause is the hoses to the center vents coming loose. Feel under the dash to see if cold air is blowing, and look to see if you can see the back of the vents to insure the hoses are connected.
Your most likely issue is a bad hvac control switch. On older cars, this was operated by vacumm pressure, but on a 2002, it is all electrical. It may be that you need to replace the whole control unit.
The selector mechanism needs repair or the doors inside the vent are jammed.
Most temp blend doors have an electric actuator. The defroster, dash vents and floor vents are usually run by vacuum.
When there is a problem with the vent system it dfaults to the defrost setting. Sounds like you have a problem in the doors that direct the air flow.
most of these door systems are vacuum controlled...but a pencil or object stuck internally can also be the cause, and not often easy to fix...for the vacuum system you can find specs and routing at the local library... check all the vacuum lines on the engine, and listen for vacuum hissing under the dash...good luck..:)
The a/c - heater controller is out...........
The vent tube has become disconnected under the dash. You'll need to remove the stereo and heater control panel to gain access. Reconnect the hose and put everything back together.
it would depend on the year of the accord. Does the defrost work or the heat in the floor work if so the line for swapping control is either broke or has come off. you can check the lower side by looking in the drivers side under the dash.
either faulty switch on dash, acutators inside the dash, or broken doors or plastic inside of dash.... common problem on the 2002-2004 or 2005 there was a total dash replacement kit it change out the broken plastic pieces inside the dash
Cars with an Automatic Temperature Control system have a thermometer in the dash console with little vents to allow air to come in. The thermometer temperature reading is then used to control the fan speed and also the air mix (temperature) to match the temperature selected....