My central AC unit has reduced airflow and I need to fix it. Blower is in the atic and the condenser is outside in the backyard (Ground level). One morning recently our condenser iced up. Discovered we had reduced airflow from the registers. We had the freon checked, it's a little low but not considerably. Filters are new. After two days of not using the unit, we turned just the fan ON - stilI reduced airflow. So I pulled the atic unit apart, cleaned the A-Coil, checked input ducts and output ducts for bloackage - clean. After reassembling the unit (and plugging it back in) the airflow was back to normal, ac was working good. This lasted for about a week and the condenser iced up again - and again we had reduced airflow. I checked the temp of the fan motor in the atic unit, warm, I could hold my finger on it for over a minute. I cycled power on the atic unit, turned just the fan on and the airflow was normal again. With my little knowledge and all the trouble shooting I've done I'm leaning towards the controller board. Any other thoguhts of what could be wrong?

I'm leaning towards worn out compressor.

Smoothy, could you elaborate? Our compressor is outside in the backyard and the fan for our air unit is in the attic. Thank you, I appreciate your reply.

The icing up problem is usually indicative of a system that is operating at too high a duty cycle (no down time to melt off ice before it builds up). Usual causes are excessively high temperatures.. low freon, or worn compressor.

I'm betting it runs almost constantly.

I'm licensed for automotive A/C systems (I'm a Degreed Electronic Engineer as well by trade)... but home systems work exactly the same. Only bigger.

Since cycling the power off then back on returns the airflow to normal, I would suspect a control problem. What you describe is a classic fan relay failing to switch the fan to a higher speed for cooling.