Why do my headlamps work on bright & not dim? on bright & not dim?

Question

Car make & Model; 2001 Ford Mustang

Answer 1

I hope this helps:



"My headlights work on bright, but not on dim" but later you say "...there was no voltage from the wht/blk wire which goes to the high beam".



I don't know which lights you are having problems with. By the way, the white/black wire goes to the lo-lights and the blue/black wire goes to the hi-lights.



If there is no voltage to the hi-light socket wire (blue/black), there are a couple of possibilities. Relay #4 may be faulty and not transferring power to the light. The dimmer switch may be dirty or faulty. The wire harness connector from the headlight switch may not be making good contact.



If there is no voltage to the lo-light socket wire (white/black), there are a couple of possibilities. Relay #8 may be faulty and not transferring power to the light. The dimmer switch may be dirty or faulty. The wire harness connector from the headlight switch may not be making good contact.



Finally, Fuse #5 should be good because there is power to one set of lights (hi or lo). You can check continuity.

There should be continuity between the blue-white and blue wires on the switch harness when the switch is in HI.

There should be continuity between the blue/white and white wires on the switch harness when the switch is in LO.



Also, if you have a Headlight Modulator that can be causing your problems."

Answer 2

Ford products have a very short life when it comes to electrical problems. But I tend to agree, the trouble sounds like the dimmer switch (Multifunction switch) on the colum. Befor replaceing it, wiggle the plug....they sometimes don't get them snapped into place at the factory...Also look for charred wireing.

If you find either of these problems contact yur dealer first! You just might be surprised!

P/S It's not uncommon to have both headlamps burned out when they are used a lot.

Answer 3

The low beam bulb is burned out or the switch contacts may be bad. It could be a bad relay under the plastic cover near the battery.

Answer 4

because the dims are burned out ..you need to replace the bulbs. be sure not to touch the glass part of the bulb when you do this ..the oil from your hands will greatly shorten the life of the new bulb.

Answer 5

this is a common problem with ford, replace your dimmer switch and your good to go! ive seen it happen a lot .hope this helps you out!

Answer 6

Swap your bulbs and see if problem is reversed then buy new light bulb, if that don't work then check manual and swap your fuses- its not hard. If that don't work, well sh*t happens