I have a 2 story home and the AC unit for the bottom floor is not working properly. Unit is running outside, but no air period is coming out of the vents. I went into the crawlspace and nothing is blocking the duct work. I opened the panel on the side of the AC unit and the coil has frost on it. I don't think it is frozen. I turned the unit off for about 20 minutes and when I started it back up, I noticed the frost on the coils was very distinct. But there wasn't any air being circulated into the duct. Not sure what is going on...

Is the blower motor coming on ? Is the air filter clean?

How can I tell if the blower motor is coming on? Is it on the unit itself?

It is the fan and motor that pushes the air through the vents. It is located in the air handler(inside unit)

The only fan that was running on the unit was the exterior fan on the top of the unit.

Then you have a problem with the blower motor. Do you hear any noise from it? Check and see if you have power to it. Motor could be bad, capacitor could be bad, cold be the relay. It is just going to take some testing. Do you have a volt meter and know how to use it?

Just checked the blower... It is working and there is hot air coming out of the square vent on the side of the unit.

Hot air as in heating? The motor is running but not coming out the vents?

The hot air is coming out of the exhaust return. No air coming out of the vents inside the home.

So your blower motor is not running. Need to test to see if the motor is getting power or if the motor is bad.

There seems to be a noise like it is running... It sounds like 2 fans are running on the unit itself. Does a fan push the hot air out of the exhaust?

Do you see ice on the evaporator coil?

After It was off for about 20 minutes, I turned it back on and frost was evident on the coil. I put my hands on it and it was really cold, it may have been frozen. But wouldn't I still get some kind of air coming out of the vents inside? I am getting no air at all when I put my hand over the vent, and the unit outside keeps running. When I was in the crawlspace it did not seem like any air was being moved through the duct work.

If it is blocked with frost or ice it can block the airflow. Let it sit off until all the frost is gone then start up and see if air is moving thorough the vent. Is the air filter clean? Have you checked for any obstruction or blockage in the supply duct past the coil near the air handler?

Filters are clean. I changed them every 30 days. Just changed last week.

I will switch it off all night and see how it does in the morning. I hope this will give it enough time to thaw if it is frozen. Thanks for your help... I will let you know tomorrow.

Pulled off side panel where blower is located. It is not running at all. I think the motor may be bad.

I think you are correct. Are you getting power to the motor? Disconnect the power and spin the motor by hand. Does it move easy and smoothly?

How do I test the power? All power connected seems to be OK...

I traced the wires and the area were the wires connect to the circuit board has a black substance on it where they connect.