[W126 Coupe] dim passenger light

[Dan Landiss]

on 3/4/2011 6:14 AM calvin young wrote:

> Dan

> Guys,

> I cannot think for the life of me what would be causing those odd 

> voltages.


Steve is right. You have a bad ground somewhere. The negative voltage 
you reported earlier confirm that. The connection you had the black 
voltmeter lead clipped to at that exact time is the bad ground. When you 
then touched the red lead to a good ground, it read negative.


>   I cannot see any relays in the lighting circuit


There are none.


> I cannot imagine that the switch would be causing this.  Mice did get 

> into the car at some point and perhaps they have shorted something 

> out, but I have looked and could not find any chewed wires.


If you had the same color wires on both sides somebody has already 
fiddled with the wiring. The alarm installer, perhaps?


>

>     Voltages are:

>     _left hand_ _right hand_

>

>     white         12.50          0.23

>     yellow         0.53          5.50

>     brown         0.23           5.55

>


What we don't know is whether that was with the high beams or low beams 
turned on. Also, the 5.55 volts on the brown wire is the bad ground you 
are looking for. The brown wires should be zero. Where are you clipping 
the black lead from the voltmeter? Are you still seeing negative 
voltages at any of the connections?


>     voltages at the fuse seem to be correct.  They are:

>     F2 high beam right 14.01

>     F4 high beam left   14.02

>     F6 low beam right    0.53

>     F8 low beam left      0.56

>


That is also a sign of shaky grounds. the voltage at an "off" lamp 
should be zero, not over a half volt.


-- 

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