Partial Transfer of Security Deposit

[Chris Eaker]

My wife and I purchased a duplex last December. Both sides were being managed by a local property management company at the time, but they only held the security deposit for one side (Unit A). Unit B is a long term tenant so the previous owner was holding the security deposit. At closing, the PM company transferred the security deposit for Unit A. The previous owner left us a $400 check at closing for the security deposit for Unit B. We thought that was the full deposit, but it came to our attention that the deposit was actually $500. The tenant showed me a copy of their original lease (It never occurred to me to ask for that before closing since it was no longer active). I have mailed the previous owner a copy of that lease and a copy of the check he gave us at closing and asked for the remaining $100. I've spoken to him on the phone about it, too. He said he sent it to his accountant, and if there is any money due us, she will send the check and not to call him about it anymore. It's been about 6 weeks and so far, he hasn't sent any money to us. I would like to send one more letter via certified mail asking for the $100 and saying if I don't receive it by a certain date, I would have to take it to small claims court. What would you do in this case?