2002 Denali Headlamps Dim

[GuMan]

My 2002 Denali low beam headlamps seem to be getting more and
more dim. I have pulled the bulb and energized it out of the housing
and it is plenty bright. I checked for excessive I-R drop on the way
in and out of the bulb, and all seems normal. I checked and even
swapped fuses and the headlamp relay with others of the same type
in the front service box. I also swapped high and low beam bulbs,
since they are the same type.

I just seems that the design of the projectors sucks. The bulbs sit
WAY back from two horizontal shutters which only allow about 1/4
of the lens to receive light from the bulb. The lens seems to be
fogged with sputtered material and the shutters and other surfaces
seems to be less than shiny. If they designed the opening between
the shutters to be this small, they should have made sure all other
surfaces in the rear of the projector lamp were highly polished, so the
light would eventually find it's way out between the shutters.

The high beams work great, as they are not projector lamps. Has
anyone experienced this? If so, any remedies? I don't think they
were this bad the first couple of years we owned this vehicle.

Thanks,
GuMan

[old_master]

Follow the wire harness from the headlamp bulb to it's ground. Make sure the ground connection is clean and tight. Sandpaper or a file works well to clean both surfaces.

[GuMan]

Thanks. The situation is this. I have a milli-ohm capable meter hooked up
to the ground line at the lamp socket. I have a 5 amp capable source running
at 5 amp compliance. I am measuring 0.674V total drop at a 5-amp current
with a volt meter place at the GND connection to the chassis, and the other probe placed at the lamp GND socket pin.

Years ago I had broken the factory connect point to the chassis GND on this
harness and applied an automotive grade anti-oxide compound. This
material should last as long as the vehicle is in service.

Seeing that I measure 0.135-ohms in the harness for the GND path, I suspect
this is not the issue. Also measured the path from the hot side of the socket
to the receptacle pin of the switch relay output. The condition is as good
there as the GND path.

At idle, the supply voltage at the headlamp relay is 13.6V. The voltage
across the lamp at idle is about 12.3V to 12.4V. I get about a 200mV
increase in voltage when the engine spins up just a little. There is no
noticable change in lighting for the 200mV increase. Alternator ripple
is very far below what would be considered bad.

Regards,
GuMan