At the vents no air is blowing. The outdoor unit runs but the evaporator coil freezes up. The blower motor is not working. I pulled the blower motor out and tested it and it runs. So the motor is good. How do I find out if my fan relay is bad? Is there something I can do with an electric meter to find out if the relay is bad? I have been an installer of heating and a/c units for 8 years and I am now trying to get some hands on with some service work.

Maybe, but check the tstat by bi-passing tie or jumper the red and green tstat wire together see if fan runs,, tie or jumper the red and white tstat wires, see if heat comes on and does the blower work,, same thing with red and yellow, does the fan come on with the a/c unit?
If all the above works by bi-passing the tstat, well ,prob. The tstat
Its possible that one speed of the blower motor is shot,also

Blower motor comes on for everything but the central air

Blower motor comes on for everything but the central air but is not pushing air out

Take relay and with an ohmmeter check the Normally open terminals - do you get continuity?

Check the normally closed - what do you get

Use that little beeping function in the multimeter

Oh yea.

Disconnect wires before doing this and make sure to label them do you don't fubar putting them back on.

If relay good and/or not obvious is there a control board? Do you get 120 or 240 at the motor on a call for cooling? How about in fan mode? Thinking you said it works in functions except cooling

You can manually put the fan in 'on' at tsat and run the switch in 'cool' to cool off. Just don't run the in 'cool' with out the blower motor working or repairs add a 0 on to the final tab quickly.