Turn signal/light control switch problem on a 1990 200.

[mike posner]

My 90 200  has come up with another test in electronic
malfunction  assessment.  This time its the turn signal stalk which works properly both up and down, but doesn't
correct to center after the turn. I'm suspecting  it's the switch
which has broken, or has it just loosened?  I hate to spend big bucks on a switch I don't need to replace.  Anybody
dealt with this?  Do I need to BOTH dx the neg batt cable
and  the red voltage line to the air bag?  I'm a bit nervous about
doing this wrong  although i did replace the magnetron on my microwave and lived to tell about  it thanks to this list>
TIA    Mike P.