My grandson got an 04 F150 for Christmas and his low beams are very dim. High beams are fine. Any ideas why?

Thanks,
Will

 

Try putting better bulbs in there.

 

What avfrog says is true. Bulbs do grow dimmer the longer they've been used. (most things wear with time and the bulb elements are no exception) I could tell if I saw them but the one other thing I would double check is GOOD ground. Easiest way to do that is make a simple (2 wire) jumper wire with stripped ends and pull one plug from rear of one headlight and go directly from bulb contacts to battery. If that headlight is appreciably brighter than the other, it's probably poor ground. If only slighter brighter, that's normal. Use at least 14 gauge wire. I'm betting it's simple aging low beam filaments though.

 

Does the truck by any chance have Daytime Running Lights (DRLs)? If so, are you looking at the relative brightness of them as opposed to when you pull back on the Turn Signal stalk to get high the beams?

 

If I'm not mistaken as with my 08 the high and low are on the same bulb so there shouldn't be any wireing issues. Jut change the bulb as the high beams may not have been used as much as low. It a 04 I'm sure they never been changed.

 

The reason I mentioned bypassing everything was to establish whether it was anything other than the bulbs. The reason I mentioned ground was because that's the 1st. thing I EVER check, with electrical issues. Auto headlights go through an extra relay on low beam as opposed to just turning on low beams, which causes a slight dimming on "Auto". After dark, turn your headlights on (low beam). then switch between "Low on" and "Auto on" and you can see a slight dimming on "Auto on". The farther the juice travels on "Auto on" and the resistance of the relay causes a loss of available power at the bulb.

 

That makes sence , didn't think about that.

 

And take it by an inspection station or dealership and have the aiming checked. Mine was way off ... way low.

You can aim them yourself with a wall and a level parking area 45 feet away from it (so that your 20 foot long truck can be backed so the headlights are 25 feet from said wall). http://www.coolbulbs.com/HID-VISUAL-...-PROCEDURE.pdf