Hello,

I have 98 dodge 3500. The left headlight is dim on both beams and I checked the grounds replaced the bulb. It only has one fuse and the right light is bright. Sockets are not corroded but the dim light is 7 tenths of a volt less then the right one measured at the socket. Could the headlight switch be causing the problem? The dimmer switch seems fine. 

Probably some ground issue. Check grounds on batterys, there is a terminal in front if driver side battery on fender, then behind driver kick panel by your feet, just pretty much need to make sure all grounds are good

Yeah I checked them already and verified the ground was good out of the socket with a volt meter. I'll pull the switch and check volts coming out.

15 hours ago, BAW said:

Could the headlight switch be causing the problem? The dimmer switch seems fine. 

NO,  You have high resistance, bad contact/corrosion, between fuse C in the PDC and the head lamp assembly.  The switch is on the ground side of the bulbs. 

Ok i'll keep looking.

Found the problem. It was a bad ground. Thanks for the help. This is a great site.

Which ground was bad...I'm having the same exact issue.

Typically headlight grounds are inside the cab on the driver side kick panel. 

The ground was located in front of the left side battery box down in the bottom. A real fun place to get to. Mine had about 11 wires attached to one stud. After seeing it, it was no wonder I was having ground issues.

Glad you found it. My 02 has maybe 6 wires on that stud. The grounds have moved over the years.

Ok, thanks guys.  I've cleaned and reinstalled the grounding block by the footwell/kickpanel...no result.  I also removed, cleaned, and replaced a two wire grounding stud just forward of the battery box on drivers fender, also no result.

 

Sorry I haven't gotten back to this sooner, but it's been hectic and doing this on my phone sucks.

Does not sound like you cleaned the right ground. if it was easy to get to, it's not the right one. The other ground is in the bottom of the inner left fender. A tough one to see, let alone get to.

Brian

I also cleaned/replaced a multi wire bundled ground low down on the horizontal in front and below the battery box, hadn't spotted that one initially.  Unfortunately, no results.  I'm adding this, in case it has relevance...my alternator has been experiencing sticking brushes, assume it is worn and time to rebuild.  Local rebuilder/repair has said it's most likely JUST in need of brushes from the look of things, but could that be playing a role here?  Battery maintains proper voltage still, as when the brushes stick I've just tapped the alternator housing to get it to engage.

Again, thank you all for any advice.

Brian, "how" did you know that ground down low was the culprit?  Did it have broken connection you replaced/repaired, or did you just clean it up and the light then worked.  I've cleaned that hard to find one up, but no bueno.

Loki,

You should start a new thread....

BUT   the ground for the headlights is G201.  (this is a 2001 manual but yours is probably similar.

 

The headlamps are sent constant 12v (even with key off.)  the headlamp switch and multifunction switch allow the bulb to "see" ground to come on.  For there to be a difference on the ground side it has to be the splice S106.  

To set up a test of whether it is the ground or the hot side, use a different headlight bulb from another car with a socket.  (I have cut a couple of these from junk cars.)  put some long leads on it.  Connect one lead from the test bulb to the battery positive, and connect the other lead from the test bulb to the suspected socket ground.  If it lights bright, ground is good and positive is suspect.  If it is dim ground is suspect.

 

Then reverse the test light bulb.  One lead on battery negative, the other lead in the suspect socket positive. 

 

Another thing that can weird out the headlamps....  did someone swap a 9004 bulb for a 9007?   I don't remember which one is correct, but the socket is exactly the same but the filaments are connected to different pins. (if you don't get it, swap the bulb from your right headlamp to your left,  did the dim bulb follow the move?)

 

GL HTH

Hag

 

 

On my truck that lower ground had 11 or 12 wires on one ground stud. At least three or four were corroded off. It was in bad shape.

Ok guys, I really do appreciate the advice.

 

BAW, I had no broken off wires, just a highly corroded fastener, hell, the terminal ring itself was not that bad.

 

HAGGAR, that diagram, like all I've found, shows the system with two 15 amp fuses...mine is a single 40 amp marked for headlamps with no others to be found in cab or under hood.

 

I WOULD start a new thread, but I am the LEAST tech savvy person on earth, and am feeling lucky just managing to navigate back to THIS thread using my phone.

 

 

Can any of you tell me exactly how this 3 pin connector is supposed to work?  The pin on the right, as seen in the pic, is dead.

That is the plug for the left,(drivers) headlamp.  The wire to the pin in question appears fine, and is tight in the pin.

 

When on high beam, that pin on the other headlamp register over 12volts, but only .52volts on drivers side.