Headlghts Again

[03blackmerc]

I replaced my LCM about a year and a half ago with an 04 MM LCM and have had no problems until now. a couple of weeks ago i noticed that one headlight is very dim on the passenger side and the other is normal bright on the driverside. inside the car the Highbeam indicator light is on but it is also very dim. when i trun the highbeams on the light on the dash illuminates bright, and highbeams work outside but still dim on passenger side. im thinking short somewhere? both foglights appear to be working fine, but ive had problems with the plug connectors in the past. could this be a bad ground somewhere?

[Curless]

Could be a bad ground, my fog light harnesses were a mess when I bought my car but no issues with the headlights at all. I would say to check all grounds on the headlight harnesses first. You could have another issue with the LCM but others on here have more experience than I do with it.

[03blackmerc]

im thinking bad ground as well. i got some cheapo eagle eye headlights a while back that came with the short harness out of the headlight. prob something to do with that

[fastblackmerc]

Definitely sounds like a bad ground.

[Rockettman]

I'm not sure it'd be a "short" somewhere.
A short will cause a fuse to blow. A bad ground won't.

[EMAS]

It is a bad ground on the dim side. The current flows through the low beam filament to it's ground contact and since it doesn't have a good path there it then flows through the high beam filament but doesn't find a ground until it passes through the high beam indicator where it does find a ground. However through all those resistors the voltage available at the bulb drops significantly thus the low output.

[Rockettman]

^^^ (DC runs negative to postive or ground to positive. Just sayin'). :beer:

[H_M_T_81]

Bad ground for sure, I have the same problem on my Jeep...and by judging how terrible the electrical systems are on these freakin cars I'm not surprised...

[fastblackmerc]

Bad ground for sure, I have the same problem on my Jeep...and by judging how terrible the electrical systems are on these freakin cars I'm not surprised...

The electrical system overall is fine. There are a few components that Ford could have done a better engineering job on.

[EMAS]

^^^ (DC runs negative to postive or ground to positive. Just sayin'). :beer:

Yes, I'm aware of that. However for most of history it was thought that it flowed from positive to negative and that remains the average Joe's perception to this day. It's also the convention used in automotive wiring diagrams. If you look at the wiring for a TPS sensor one pin is Vref ie 5v, another the variable signal, and the 3rd, the ground, is labeled sigrtn for signal return.

[03blackmerc]

I unplugged all the conections i could see from under the hood. I found the plug end for the dim side bulb was melted pretty badly. i replaced both plug ends on either side and installed new stock style bulbs with bulb grease. i was using Hologen bulbs during this meltdown. Both headlights seem to be bright now, both highbeam lowbeam work. When driving at night i still can notice the highbeam indicator light on the dash illumintated very very dim, can barley notice it, could this have anything to do with the foglights? i feel like the foglights are a never ending battle of bulbs and corroded plugs. not only that the foglight housings them selfs are started to fall apart, the reflective foil on the inside in starting to peel off inside the housing. should i replace these bulbs to? Anyone know of any good replacement housings?? where else could this fault be? thankyou for your input

[EMAS]

If your high beam indicator is still on even dimly when your low beam headlights are on then you still have a ground that is not 100% perfect. You didn't connect the new pigtails with insulated crimp connectors (guaranteed failure points) did you? Also how far back did you splice the wires, was it good shiny copper? Copper conducts heat pretty well so if the connection was bad enough to cause the connector to melt it can damage the wire inside the insulation pretty far up.

[03blackmerc]

wires looked good not corroded, i agree with the bad ground but all connections look fine up to the main harness. i did use insulated waterproof butt connectors nicely wrapped in electrical tape. I know prob. not the best chioce but never failed me in the past. plus these wires are in the headlight housing that has a o-ringed seal. Could the melting issue be caused by the hologen bulbs? also the plastic around the center pin of the bulb plug was melted on both bulbs. I think the brand of the bulbs are HKG i remember them being very cheap lol

[EMAS]

The melting was most likely caused by a poor connection that caused it to heat up.

[LSp8]

I'm having this problem right now (exact same thing) and its really pissin me off. Just had the LCM replaced in 2012 and now I'm 100 miles from my house and on a very restrictive budget. Not sure what to do now. If I wiggle the wire from the passenger side headlight socket the light dims even more. What causes this foolishness? I don't want to keep driving around like this but I don't have a choice right now.

[RF Overlord]

Not sure what to do now. If I wiggle the wire from the passenger side headlight socket the light dims even more. What causes this foolishness? Read the entire thread.