Resolved Question: Can you answer my question regarding my son?

Please bare with me on this question. Its long, but kind of important. Lately my grown son and I haven’t got along- he is 22. I have tried to reach him but he refuses to answer my calls. One minute everything was fine and he had sent me a birthday present and the next minute he either ignores my calls or doesn’t even bother to talk to me two seconds and says he cant talk(in a rude way) and will call me,but never calls. This has me heart-broken. I know part of the reason why he has avoided me,he defaulted on a car loan which I co-signed on. Of course this upsets me,but not to the point in which it should ruin our relationship as Mother and Son. I have also been sending him any money I can to help him get through some tough times which he has pulled out of. He works steady and has his own place. He did stay for awhile with my Brother but this didn’t work out. I raised him as a single parent and I know for sure he is working steady and I think still has a girlfriend. His father abandoned him and never was in his life as a child. We have had are problems,however,this is the first time he is avoiding me. There were issues with him before(as a teenager) regarding discipline and being obedient to me. But he stayed with me until he was 21 after a brief period when he moved out and lived with roommates. This situation didn’t work out due to all of them lacking in responsibility and not paying their bills. But when he lived with me, he worked full time and helped pay some bills. I gave him freedom and only asked that he not abuse alcohol while drinking. And he seemed to have his life together when he was working a lot. But now this. Can you offer your opinion to a sad Mother? And how do I let him know that this behavior is unacceptable and disrespectful without losing him completely? Oh by the way I will be moving back to my home state next year to live near him. This move was due to personal family reasons(a death in the family) and I have decided to stay her to attend school before returning home. So I would lkike to clkear these problems up between us.