98 acc ex/4 a/c center vents no air, only sides and bottom. cleaned buttons, still no center air. was blowing fine before turned on defrost and warmed temperature for cold rainy night..

 

I've moved this to General Tech.

First question, does this have manual or auto HVAC?

Sound like an issue with the mode control motor but that is a guess......Replace NOTHING on a guess.

 

Try selecting floor and upper vents (2nd button?) and then return to upper vents only. This works for my 94EX.

The mode control motor is on driver's side of heater core module. You can use mode control buttons to locate the motor and determine if no movement is occurring when upper vents is requested. If no movement occurs, you will need to check for voltage to the motor w/ backprobe. If no voltage, panel selection switch is faulty. If you have voltage, then mode control motor is faulty.

Suggest downloading an accord manual from Online Manuals post in DIY forum for detailed guidance and pics of assy. A better manual is available from automanualsource.com for $22.

It will be challenging to remove working under the dash on your back.

good luck