Expert: Sean Halliday - 6/4/2006

Question
All controls appear normal [heat&ac will come thru vents at highway speed]. I removed the blower motor and bench tested it works great!   No blown fuses, but no power to blower motor. What am I missing?  

Answer
you say the controls appear normal...what about the regulator?and also the CC unit on the dash,,,,,,,i have seen these units fail on newer mercedes,,,the climate control unit.unfortunately these things are expensive,,,the regulator/resistor(speed regulator) usually is on the blower motor.The only way to be sure is get it tested at a reliable electrical shop.otherwise you will have to do it yourself.my bet is the CC unit.on the dash,,,can you "borrow" a used one to check?theres really no other way to test these things.trial and errror on the heater control unit is the only way but 99% is the unit on the dash...