I had this with my '98 passat. The indicators and hazzards became intermittant and occasionally wouldn't work.
The hazzard warning switch in the dash controls the indicators and hazzards. All you need to do is replace the unit (costs about £16 from a main dealer and you can replace easily yourself)
To replace; remove the blanks above and below the Hazzard switch in the dash and (gently but firmly) prise out the hazzard switch.
The new unit will just push in place 
Hope this helps :-)
                
 Kip
                
 December 2006