My lennox central air system is about 10yrs old. It worked all winter as far as the furnace but when I tried the air it didn't. Everything appears to turn on, the outside unit works, the inside condenser works, the only thing is it does not blow air in the house. Can you advise me so I don't have to spend hundreds on a service call if I could fix it myself. Thanks

Then the blower, or blower relay/contactor may have failed.
Does the Blower work on Heat?