They entered service in August 1959 from Ayr depot and were mostly used on Glasgow to Ayr, Girvan and Stranraer workings, but could also on occasion be found on Largs and Ardrossan services. Initially services ran out of Glasgow St.Enoch station, when it closed the Ayrshire services were transferred to Central station.
Originally it wasn't planned to use the vehicles on the Stranraer service, this was a decision made just before the vehicles were delivered. Once this decision was made the two buffet cars were ordered but couldn't be fitted into the build programme at Swindon till later. The Stranraer services were known as the boat trains as they connected with the ferry to Larne (Northern Ireland) at Stranraer Harbour station. These were normally six-car formations. The buffet cars were not a success on the service and were soon transferred to Edinburgh and Glasgow services.
The image shows the Glenwhilly signalman heading back to the signalbox as the 10.42am Glasgow Central - Stranraer Harbour continues through the closed station on the 10th August 1973. Michael Mensing.
Although the intention of the two cab types was to allow access throughout a six-car formation, connecting DMS to DMS, in practice it seemed that sets were rarely in the correct sequence for this to work.
As can be expected, excursions saw then visit unusual places such as Perth / Dundee, and the Callender / West Highland Line on a Six-Lochs Land Cruise, and also maintenance needs also saw some visit Inverurie Works (although Glasgow Works did the majority of the heavy work).
Mass withdrawals happened in the early 1980s, all the class being withdrawn by the end of 1982. However two sets were re-instated and lasted until January 1983. Although used on various other routes out of Glasgow in their final years, these 126s remained closely identified with the Ayr line until displacement by a mixture of loco-hauled trains and other DMUs. After withdrawal two sets moved to undercover storage in Dunfermline Townhill depot so preservationists could select the three vehicles they wanted.