From: muratlanne@gmail.com   
      
   "Jim Wilkins"  wrote in message news:10ak3rg$krco$1@dont-email.me...   
      
   ...I replaced the multifunction switch on the   
   column which showed some suspiciously high resistance readings after 150,000   
   miles. ...   
   --------------------------------   
   That is a known issue with switch contacts. The oxide buildup shows   
   resistance at the low voltage and current of a DVM resistance measurement   
   but not so much at its higher normal working voltage and current, which   
   "punch through" the oxide at least temporarily. Those contacts still lit   
   turn signal bulbs brightly (my test lamp). On a high end Keithley 580   
   Micro-Ohmmeter there is a setting that limits the test voltage to 20mV to   
   measure the resistance of the undisturbed oxide.   
      
   Switches meant for low voltage and power usually have gold-plated contacts   
   that don't oxidize, the better switches for higher power use a   
   silver-cadmium alloy whose oxide is conductive. Gold-plated "dry contact"   
   switches can be damaged by arcing if opened at higher power levels.   
      
   The contacts in starter motors I've fixed had thick copper contacts which   
   had burned away enough to no longer connect. I built them back up with   
   brazing rod which lasted 40,000 miles, twice.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)