Mechanics

MERCEDES , CHANGED BATTERIES IN BOTH KEYS AS THEY STOPPED WORKING. ONE KEY LASTED 4 WEEKS. THE OTHER IS BEGINNING TO GIVE TROUBLE AFTER 3 DAYS.

2001 Mercedes Benz C320 • 125 miles

Mercedes 2001 c320, changed batteries in both keys as they stopped working. One key lasted 4 weeks. The other is beginning to give trouble after 3 days. Other problem that has been occuring alongside this is that the battery drains off within one or two days of no use. Battery itself has clear window that indicates it is still good. When putting the negative lead back on after charging battery significant draw is evident. Don't know if this is related to the key problems.
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Johnthemachinist
October 12, 2011.



I have often heard that after time the buttons on the fob wear out and can keep a slow draw closed circuit. Not enough of a signal to actuate any functions, but enough to drain batteriws. Also after time corrosion such as copper build up will mkae the circuits run hotter and demand more energy to function as this couses more resistsnce in the circuit.
A quick fix that might help some until you can get new buttons and examine the circuit borads is to take a standar pencil eraser and clean the battery contacts.