I have an '04 Lariat. With the lights on auto, the low beams are very dim/yellow. the fogs are very bright though. When I turn on the high beams they are extremely bright. With low beams on auto, i can flip to on position, and they get noticeably brighter. On high beams it makes no difference whether the switch is on auto or on. Why are my low beams dim on auto, but not on ON. I have a new set of regular Silverstars, but it has been the same with all bulbs we have tried.

 

I would like to know the same thing, mine is doing that also.

 

Have you checked the wires in the back of the plug? Maybe there is a connection issue

 

Checked when i put in the new bulbs.

 

Mine where doing that also when I got my truck I had the stealership fix it for free since it was a hazard to drive the truck like that at night but they told me it was a bad connection on a wire harness. How true it is may be another story

 

Is there anything I can do myself?

 

anyone else?

 

Sounds like a bad ground. You'll have to find a schematic of the switch and circuit. If you have a voltmeter you can check the voltage at the bulb socket in the auto and manual position. If you do not have a notable voltage drop its likely a ground issue. If you do have a notable voltage drop its likely the switch or a relay in that circuit

 

Each circuit has it's own seperate ground (I.E. the low beams have their own power and ground lead, and the high beams have their own power and ground lead. Since it's the low beams giving you the dull yellow type light, you only need to identify the wires (color code) for the low beams, along with the "auto" light switch setting.

I don't have my factory Ford schematic handy, so perhaps someone will chime in, or you could try the search here and see if this circuit was already posted. Then get your trusty multimeter and start checking voltages for the drop.

 

OK guys, i fooled around with my multimeter and I found:

Low beam ON position- 11.9 volts
Low beam Auto position- 11.3 volts
High beam On position- 12.4 volts
High beam Auto position- 12.4 volts

I put the meter on the ground in the light socket and the ground post on the battery with a <.1 volt drop, so unfortunately the ground is the problem. All tests were done with the engine OFF. I looked for a schematic, but no joy, so where do I go from here.