My honda SM4's blower fan motor has a resistance of 0.8 Ω, & mostly used @   
   7½ v when alternator @ idle rpm produces 13½ v, i.e. 6v is wasted as heat by   
   these resistors which presumably have a total resistance of 6 ÷ 7½ x 0.8 Ω   
   = 0.64 Ω, i.e. #    
   of watts wasted must be 6v x 6v ÷ 0.64 Ω = 56¼ watt.   
   In Dec'12 I noticed a Mercedes 350 has the same problem ( like cheaper cars   
   have ) of heat inside users' space when aircon is off, i.e. no buck converter   
   is used to reduce blower fan motor's voltage, so these resistors heat up this   
   space even after    
   aircon is switched off.   
   Does any car maker use a buck converter to reduce this voltage ?  Does any1   
   know where I can buy a buck converter with easily switchable output voltages   
   of 4, 6, 9 & 12 v, of ( 12 ÷ 0.8 Ω = ) 15 amp, to replace these wasteful   
   resistors ?   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)