A few weeks ago I changed the outside unit's starting capacitor and that got the fan on that unit to rotate and the air conditioning on the enclosed back porch started working.
Today I came home and the main part of the house was hot. I turned down the thermostat in that zone but I still didn't feel any air blowing out of the registers. I changed all the air filters but still didn't feel any suction at the filter housing or any air coming out of the register.
I had my wife turn on the air conditioning via the thermostat while I was downstairs listening at the inside unit. I heard a sound like a refrigerator or dehumidifier kicking in and then a few seconds later I heard the sound of a fan starting up.
I removed the cover over the fan and taped the safety switch and turned on the air conditioning and I can definitely see the squirrel cage fan running and it looks and sounds normal.
For what it's worth the fan on the outside unit for this zone seems to be spinning normally as well.
How on earth can I not feel any air coming out of the registers or feel any suction at the air return? The only thing I can figure out is that the fan seems to be running normally, but is actually at a lower speed than normal. It sure looks normal. I don't see any gaping holes in the ductwork or anything.
I've changed the fan on my furnace in a previous house a few years ago, so I'm somewhat familiar with what they should sound like. The inside unit is a York affinity 9.V series
Here's a video of the fan running.