The 51-year-old Dubliner is 11-under-par for the event and currently one shot off the clubhouse lead of Scotland's Grant Forrest at the DP World Tour event.
Harrington is bidding to become the oldest winner in the history of the DP World Tour by eclipsing Miguel Angel Jimenez's current record of 50 years and 133 days.
After a first round of four-under-par 68, he struggled to a one-over-par 73 on Friday.
Today, Harrington made a good start, finding the par-five second hole in two strokes to make his first birdie.
He found the right rough with his opening two shots on the par-four sixth hole but then chipped in for birdie.
Making the turn in 34 strokes, the Dubliner hit form to birdie six holes in succession, starting on the par five 11th hole.
Harrington hit his approach shot on the par three 17th hole to 16 feet but had to settle for a par.
After finding the fairway on par-five 18th hole, Harrington got his long shot within pitching distance of the green.
He left his pitch shot under the hole but was unable to convert the 13-foot putt, carding eight-under-par 64.
Speaking after the round, Harrington said that patience was the key.
"When good things are happening to you on the golf course, it's a lot easier to be patient and wait for your run," he said.
"I didn't even know that I made six birdies on the back nine. It's just nice."
Asked to explain how he has maintained his longevity in the game, Harrington had a typically comprehensive answer.
He told Sky Sports: "The game has changed and will be changing forward. I would have been one of the first guys who started in the era of Tiger's big money to have a full-time physio and a full-time trainer.
"I would have looked after myself all the time. Just a different lifestyle and I think there's a lot of players who will get to 50 years of age fitter and stronger.
"The biggest problem is burnout. I was burnt out five years ago. I'm out here because I've nothing else to do.
"I've figured out that this is what I like doing and I'm good at it. There's no point trying to do something else that I'll have never be as good at as I am at golf.
"So why not find a way of loving golf again. It did help me a lot on the Champions Tour but even before then I realised I needed to change my golfing personality."
He added: "I was in contention a lot last year and I feel comfortable in having a chance and taking on the shots."
While without a win on the DP World Tour since the 2016 Portugal Masters, the three-time major champion won four times on the PGA Tour Champions last season to rediscover the winning feeling.