Lifetime Premium Member
Date registered: Nov 2002
Vehicle: 2003 G500, 2000 SL500, 1995 E320 Cabriolet, 1980 TR8
Mentioned: 6 Post(s)
Quoted: 96 Post(s)
If the headlamps no longer come on, but the high beam indicator light does when the headlamps are set for low beam, then I would look into a bad ground in one or both of the headlamps. In particular, look for corrosion in the wiring or the actual headlamp socket. As the headlamp ground connection resistance becomes higher (due to the corrosion), more and more of the lamp running current tries to return to ground via the high beam filament and circuit (the high and low beam filaments for a resistive voltage divider). The only pathway for that current flow is through the high beam indicator bulb which will cause it to light. An easy test for this is disconnect both headlamps and see if the high beam indicator lamp functions normally.
Floobydust: a contemporary term derived from the archaic Latin miscellaneous, whose disputed history probably springs from Greek origins (influenced, of course by Egyptian linguists) - meaning here "a mixed bag." - National Semiconductor Audio Handbook