As part of the modernisation of the West Coast Main Line, which included electrification, 100 locomotives of five types were acquired from different manufacturers. Ten Class AL4 locomotives numbered E3036 - E3045 were built in 1960 to a design by GEC by the North British Locomotive Company in Springburn, Glasgow. Locomotive E3040 worked the inaugural AC electric-hauled train from Manchester Piccadilly to Crewe on 12 September 1960.
Power supply
The locomotives always worked on power provided by overhead catenary energised at 25,000 V AC. However, the main transformer, normally operated with the four windings in series, could be operated at 6250V AC with the transformer windings in parallel. This voltage was initially to be used where limited clearances gave concern over use of the higher voltage.
Rebuild
Problems with the mercury-arc rectifiers plagued this class and in 1962 E3036 was returned to GEC, the builder of the electrical equipment, in an attempt to find a solution. Within a year, all ten were out of service for repair. The problems persisted and in 1967 they were once more placed into storage, using the former steam shed at Bury, along with Class AL3. During this time E3043 went to Rugby Testing Centre for trials.
Reprieve
The persistent problems could have been the end of the ten locomotives of Class 84, but the extension of the West Coast Main Line electrification to Glasgow meant that more electric locomotives would be needed. It was therefore decided that the stored Class AL3 and AL4 locomotives would be repaired, which was conducted at Doncaster, and returned to service, with a lower number of Class 87 being built.
Rebuild 2 and renumbering
Between 1971 and 1972, all ten locomotives were rebuilt with silicon rectifiers and dual brakes, and were reclassified under TOPS as Class 84, being renumbered 84001 - 84010.
The end
The second rebuild failed to overcome some of the more persistent problems and British Rail decided in 1976 to withdraw them from service. The first to be withdrawn was 84007 in 1977, the last 84003 and 84010 in 1980.
After withdrawal
84003 and 84009 passed to the Research Division: 84009 was rebuilt as a load bank tester and 84003 was used as a donor loco. They were given departmental numbers ADB968021 and ADB968022 respectively, although the latter was never applied. In 1995 84009 was broken-up following withdrawal from its load bank duties; one cab of this locomotive was saved together with a quantity of spares. 84002 and 84010 were purchased by GEC for experiments, but scrapped soon afterwards. 84001 was moved to the National Railway Museum in York on long-term loan. The original intention was to eventually swap it for a more representative Class 86, but in 1994 the locomotive was officially claimed for the National Collection. In the intervening years, the 84 had become important to the Museum as the sole-surviving post-steam, main line example of a North British Locomotive Company product. 84001 remained at the NRM until 2000 when it was loaned to the AC Locomotive Group for an initial period of three years, later extended by five years, in exchange for much-needed cosmetic restoration work being undertaken. It continues to carry BR blue livery, as expensive cosmetic modifications would be required to return to "as built" condition in electric blue livery.
