I am restoring my FS1E-DX, I have had since 1979, (R reg) and have found Ebay to be a mine field for parts thanks to the newer models.
So assuming the original wiring diagram in the Haynes manual would be for the earlier Fizzy's You should invest in a multi-meter (can be bought for a Fiver) and with indicators running, test any spare/loose wires for a similar intermitant contact.
Have you asked the question on the FS1E home page? http://www.fs1e.co.uk/