Joe, freezing can be caused by "failure to start".
Most newer systems have a set of conditions they must meet to complete a cycle. If they "fail to start", they go into a CRC. Some take so long to complete their CRC, the compressor will freeze up.
Does the small blower run before the system?
Does the system begin to blow and then shut down...before the compressor is covered with ice?
Does the control board have a LED disagnostic tool ( lights in an order )?
These could get you started.
Something as stupid as a hunk of hair in the blower cage can cause the motor to draw too much current...thus faulting the controller.
If you have already talked about all of this, sorry for taking more of your time.
