[W126 Coupe] Passenger headlight bulb only glowing at half strength and it is not the bulb

[Gerry Van Zandt]

First, check the fuse to make sure it's making proper contact.

Second, have you tried replacing the bulb?

Third, if the bulb is OK, you may want to get a multimeter and measure voltage at the connector at the back of the headlight.  At the same time, check the connector (make and female sides) for signs of corrosion or other crud and clean with a wire brush if you find anything.

Fourth, check your battery terminals to make sure they are clear and not causing any issues with poor or intermittent contact.  Measure your battery voltage with the car both running and off.  Should be 12-13.5V ish.

Fifth, check your ground point behind and below the headlight (typically brown wires going to a single screw) to make sure that it's making proper contact and there is no corrosion there.

Let us know what you find.  One of these solutions should identify the problem.  If it doesn't, then you may have another issue like a voltage regulator or even an alternator not generating the proper output, but that's a more serious bridge to cross if everything else checks out OK.

Cheers,
Gerry



On Feb 18, 2011, at 11:15 AM, mbcoupes-request at mbcoupes.com wrote:


> 

> Hi guys,

> 

> I could use some help with a light problem.  It seems my left headlight is 

> glowing dim.  the light is half of what it should be.  This problem seems to 

> come out of nowhere although the mechanic is changing out the driver's door 

> and working on the wires.  He may have shorted out something, perhaps this 

> caused a relay to malfunction.

> 

> Changing driver's bulb for passenger bulb changes nothing.  Anyone had or 

> heard of this problem before?

> 

> Cal