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.
The Half a Game initiative is currently sweeping across Wales and proving a major success. The scheme aims to give every young player at least half a game every weekend. WRU TV recently visited a festival in Narberth where clubs have fully embraced the initiative.
Both Bargoed and Swansea were seeking their first win of the Principality Premiership season this afternoon. It proved a fruitful day for the hosts - not only did they win, but Bargoed claimed a try bonus point.
Cardiff managed to keep their unbeaten record at home intact, but only just as Bridgend made them work extremely hard before the Blue and Blacks secured a hard fought Principality Premiership win at the BT Sport Arms Park last night.
Former Wales back row Andy Powell gives a guided tour of The Wern, home of Merthyr RFC, who are determined to prove a lot of people wrong and make their mark in their first season in the Principality Premiership.
Wales Sevens head coach Gareth Williams looks back on the Rio Sevens success where he helped GB win silver. He believes the successful campaign is a huge boost to his Welsh squad as they prepare for another World Series, as WRU TV's Graeme Gillespie discovers
British and Irish Lions head coach Warren Gatland will be heading back home to take on the All Blacks next year where for him, success for 2017 is all about going to New Zealand and winning a Test Series.
Last week all roads led to Eugene Cross Park where defending champions Ebbw Vale hosted this season's launch of the Principality Premiership. WRU TV's Graeme Gillespie was there to capture the thoughts of Damien Hudd, captain of Ebbw Vale, and WRU Head of Performance, Geraint John.
Llandovery made it three in a row when they defeated Aberavon in the final of the National Foster's 7s at BT Sport Cardiff Arms Park on Sunday. On another eventful day of sevens, Newport claimed the Plate and the Dragons won the women's crown
Last week saw Cardiff welcome players from around the world for the 21st Golden Oldies Festival. The tournament features players over 35 years of age, and this year's event saw a select few represent the WRU in a 'friendly' against the Wooden Spoon.
Wales Under 18 captain Callum Bradbury is delighted to have seen his side claim a narrow 18-17 victory against a strong SA Schools 'A' side to end the three-match Under 19 International Series in South Africa on a high note.
The Wales U18 squad spent an emotional day in the drug-riddled townnship of Hout Bay. Hout Bay Warriors President Fred Johannes said the visit was 'the talk of the town' and will dream about the day everyday for the rest of his life.
RGC 1404's new head coach Mark Jones is hoping to build 'something special' in north Wales and is already looking forward to the development region participating in the Principality Premiership for the very first time.