Lighting and air-conditioning on board the Dublin service failed
Irish Rail has apologised after customers were stuck on a train for seven hours.
Lighting and air-conditioning on board were also out after a major mechanical fault on the line.
It happened between Mallow and Charleville on Sunday.
The Cork to Dublin train was due to arrive in Heuston Station just after 7.00pm - but it did not get there until 11.00pm.
Barry Kenny from Irish Rail says major interruptions like this are rare.
"not only was the train immobile, but lighting and air conditioning were also affected.
"That was obviously why we needed to ensure we transferred the customers to another service because it was becoming very uncomfortable for customers onboard.
"It appears to have been an electrical power fault that immobilised the train - but also the power systems on board.
"It has been many years since we had a delay of this scale, and obviously we very much apologise to customers".