Upon arrival, found the blower fan not operating for the upstairs spare room air handler. This caused the system to start to ice up in cool mode. Found 24 V at the board for call to fan. Found 120 V at the relay and at the blower fan. Blower fan still inop. Between the relay and the blower fan found no voltage. While I was working and testing out the control board, I had not moved any wires but the blower fan started working out of nowhere. It seems the control board at the air handler has an intermittent issue with the timer delay on the relay for the fan. The control board at the air handler will need to be replaced. Provided customer with estimate to replace the control board at the air handler. Due to the age and state of the system, replacement options are recommended at this time.