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Ask Dodgerench Your Own Question
Dodgerench, ASE Certified Technician
Category: Dodge
Satisfied Customers: 3404
Experience:  30+ years Dodge/Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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I have a 2004 Dodge Ram 1500, the passenger side headlight

Customer Question

Hi, I have a 2004 Dodge Ram 1500, the passenger side headlight works but, the drivers side does not. I replaced the light switch with a brand new one, what is the problem and how can I fix it.
Thank you
Submitted: 1 year ago.
Category: Dodge
Expert:  Dodgerench replied 1 year ago.

Hi, welcome to JustAnswer!. This is Ed.

I have to play the probability card tonight, William.

Headlamps are triggered by a common source, which is an input from the headlamp switch to the Front Control Module (FCM). One input is used to turn both headlamps on, so if one works... the FCM is getting its information from the switch.

Next, is it both high AND low beams that are out on the driver's side?

If so, you've tested two separate output drivers from the FCM. Between left and right sides and high/ low beams, you have four separate drivers that control these two headlamps through their high and low beam functions. I doubt that there would be two drivers failed on that one side at the same time because it simply doesn't happen. Instead, I figure you probably lost the ground circuit shared by the left side high and low beam bulb.

Check the center wire of the driver's side bulb to see if it has voltage with the headlamps turned on. Being a ground, it should have little-to-no voltage if OK. Color of the wire is black/ light blue and it shows to be the center of the three wires in your bulb connector socket.

And speaking of probability... rodent damage is the #1 cause of this sort of thing. Inspect wiring and the underhood area for signs of nesting or "chewage". Let me know what you find and we'll continue from there.

Good luck!