Despite leading 19-0 until the final minute of the opening half, the Wizards struggled to overcome a spririted Llanharan outfit, who were fit and played withgreat heart.
Early tries by wing Richard Carter and centre David Hawkins were followed by a second from Hawkins with two converted by Jamie Davies.
Llanharan got on the board with an injury-time penalty by Wayne Jervis, but within five minutes of the restart, Carter went over again for Davies to convert.
Llanharan replied with a try by hooker Alan Williams and Jervis kicked a penalty, though Davies added a further Aberavon score with a penalty shot.
Aberavon were rocked again when flanker Ceri Jones went over for a last-minute try that Jervis converted from the touchline.
In Division One, leaders Maesteg won a local derby by 37-15 against Bridgend Athletic and scored five tries through wing Alun Brown (2), centre Paul Morgan, veteran scrum half Kevin Ellis and fly half Mark David.
David converted three and placed two penalty goals, but the Athletic responded with tries by Gavin Pound and Andy Tollentino and skipper Stuart Morris placed a conversion and penalty.
Carmarthen Quins are holding an exhibition to commemorate club players who fought in World War I. All welcome to the clubhouse on Friday afternoon to learn more about local history, or share any family anecdotes or artifacts.
Defence coach Shaun Edwards believes Saturday's clash against England - the 'form team in world rugby' - poses a huge challenge for his side but he is confident, with Wales beginning to show the defensive qualities displayed in the last two World Cups,