New (used) LCM. Headlights turn on, then off immediately.

[baneoh]

Hi y'all,

I posted yesterday about installing an LCM 4 in my 1998 540i. Everything went according to plan, and all the functions seemed to be working until I turned on my low beams to drive home from work last night. They came on just fine, then shut off. I can turn them off and back on and either one or both of them come on for a second or two, then turn off. Halos, high beams, and all other functions seem fine. Did I just get a bad LCM from the junkyard? Or is there a way to fix this by coding? I'm guessing it's just another bad LCM, but I figured I'd ask here first before I drag my butt back to the junkyard.

Thanks

[Chedley]

May be it is the low beams / light bulbs that need to be replaced...?

[PanzerShrekd]

Mine did that when the ballasts started to go, if you have a junkyard near you try new ones.

[baneoh]

Mine did that when the ballasts started to go, if you have a junkyard near you try new ones.

Interesting. I wonder why both ballasts would go at once. Also, right after I replaced the LCM with a used one. My first thought is that the used LCM is bad. But after driving it for a few days I also noticed that it only happens when the car is running, and only for a few minutes after I start it. If I futz with the ignition switch and light switch, I can get them to stay on. Last night they were fine for the 30 minute drive home from work. Seems like a voltage issue?? But why would it rear it's head only after I changed the LCM???

Sometimes one headlight goes out, sometimes both. Sometimes one looks like a different color than the other. This is weird guys.

[BimmrMeUpSnotty]

Color changes? That’s a voltage issue and the ballast is reacting by not providing the correct juice to the HID bulb. Kinda like when a ballast is going bad. Test the voltages coming into the ballast with a meter, write it all down.

[baneoh]

Color changes? That’s a voltage issue and the ballast is reacting by not providing the correct juice to the HID bulb. Kinda like when a ballast is going bad. Test the voltages coming into the ballast with a meter, write it all down.

Will do.

Would the LCM be responsible for regulating the voltage in any way? Or is it a fault somewhere else?

[BimmrMeUpSnotty]

Could be, I’d check all the grounds first, then the rest of the wiring.