I spent several hours chasing a "master warning light" on a Mercedes coupe. This one was a big red rectangular warning light in the middle of the dash with a big exclamation point on the lens- - - - -impossible to ignore! The wire powering the light had a particular color code that went everywhere- - - -under the dash, into the engine compartment, under the vehicle. etc. After about 6 hours of unwrapping wire looms and chasing circuits I discovered I could turn the light off by jacking up the front of the car about six inches. More troubleshooting with no results. I finally found a wire with the same color code leading into the top of the brake master cylinder- - - - -to a float valve.
ADDING TWO OUNCES OF BRAKE FLUID TURNED THE LIGHT OFF!
The car owner was a doctor who owned the local hospital, a really good customer who kept me busy maintaining six cars his family owned- - - - -he got a freebie that night, and I learned an expensive lesson!
Jerry
Filthy German engineering.
Carl
