Class AM1 was allocated to the prototype AC electric multiple units, converted from fourth-rail DC electric stock in 1952 and used on the Lancaster/Morecambe/Heysham route. This route had been electrified by the Midland Railway at 6.6 kV, 25 Hz AC. These were withdrawn in 1952 and the service reverted to steam haulage. The line voltage was changed to 6.6 kV at 50 Hz in 1953 and the AM1s were introduced. Thus was a test to see if power could be drawn from the National Grid rather than railway owned power stations. The AM1s were fitted with mercury arc rectifiers but one was later converted to a solid state rectifier as a test. The stock was maintained at Meols Cop works near Southport.