The 104 is an unsual route with a history thayt goes back two decades. However the current version started in 2000 and since then has gone through many changes as outlined on the overview page. My first proper trip on the 104 was in 2011 when it was routed from Clontarf Garage to Ardlea Road in Artane via Donaghmede and Beaumount Hospital. The bus also went north from Clontarf Garage and followed the 130 part of the way to the CRC in Clontarf. On that day I travelled on AV 417 of Clontarf Garage.
The changes to the 104 in 2011 only lasted a few months and in early-2012 the route was modified again. This was connected to the Network Direct changes to the 3 and the 16, but occured first. The route was taken out of Ardlea Road and extended west to Shanard Road in Santry, close to Omni Park Shopping centre. It also took a simplified route from Killester to Artane and operated on a hourly-frequency Monday-Friday. When the buses of the GT-class were allocated to Clontarf Garage in 2012 this was one of the first routes to be converted to dual-door operation. On the 2nd May 2014 I travelled on the 08:00 104 from Clontarf to Santry. I did not expect anyone else to be on it but the load peaked at 14 passengers, picking up people along the route in Clontarf, Killester and Beaumont. Most people got off at the second-last stop in Santry and evidently going to Dublin City University on nearby Collins Avenue. It was probably the highest loading I saw all day on the route and two double-deckers assigned to it seems like a waste of resources.
The current 104 is the only bus to use certain stretches of road such as the lower part of Castle Avenue in Clontarf, Collins Avenue in Killester and Kilmore Road in Artane. It shares some routing with the 130 in Clontarf and the 1 in Santry. In fact it shares a terminus with the latter on Shanard Road.
On the day I travelled on GT 117.