Blower works but no air through vents
2006 Honda Civic, airflow coming out of the vents drops to barely trickle, turn it off and restart and A/C blows cold and hard.
The key to diagnosing this problem is the lack of airflow. That’s a classic sign of a low refrigerant charge that’s causing evaporator freeze-up. When a system is low on charge, the refrigerant entering the evaporator coil immediately boils and creates a super-cold spot. Humidity in the air condenses on that cold spot and forms ice. The ice dam gradually spreads upwards on the evaporator coil, eventually blocking almost all the airflow. When you turn the A/C off the ice melts and drains out the condensate drain. When you start the A/C again, the cycle repeats itself.
You can try adding refrigerant with one of those do-it-yourself kits, but keep in mind that these R-134a systems can be easily overcharged. And, when it comes to R-134a, more is not better. Overcharging actually reduces cooling. If you’re not sure how much to add, take your vehicle to a pro.
If you experience intermittent cold/hot A/C performance, but don’t have the same reduced airflow problem as this owner, don’t assume its low on refrigerant. Intermittent cooling without reduced airflow can be caused by a faulty expansion valve, bad compressor thermal protector, or a worn compressor clutch. Adding more refrigerant won’t fix the problem. Diagnosing the actual cause and replacing the right component is a job for a pro.
© 2012 Rick Muscoplat