[Mgs] MGA Turn signal puzzle

[Robert J. Guinness]

I have an MGA 1600 with the pnuematic turn signal switch on the dash 
(Moss #162-400), and the barrel type flasher unit on the firewall (Moss 
# 141-750).  The pnuematic part of the turn signal switch never worked 
so I just hold it to the side until I finish my turn. Recently, holding 
the lever only initiates two  --  and only exactly two  -- blinks on the 
turn signal lamps.  The same thing happens with the front and back lamps 
and on either side.  Is this a turn signal switch problem, or a flasher 
unit problem?  Is there a diagnosis protocal to follow to isolate the 
problem?  I never repaired pnuematic turn signal switch because one of 
the screws holding the case of the switch together is stripped (the head 
is intact, but it and turns freely in the threads without moving out  
--  most curious).  Thank you.
-- 
Robert Guinness