One Halogen Light Out - Not the Bulb!

[brettbimmer]

Hi Fam:

So I was driving home in the dark yesterday and turned on the Trifecta Light Mod (thanks again BP!), and a few miles from home I get the cluster warning telling me that I have a headlight out. Car has Xenons as primary lighting with the halogen as the passing, DRL, or extra light with brights with coding. Figured that it was probably just a bulb, but after taking the old one out and installing a new one, still no light on either Trifecta bright setting or with all lights off and pulling the indicator stalk back, as one would do to signal a pass, etc. Oddly enough the passenger side is working fine in both cases.

Side notes - car has 62,000 miles on it, and I have yet to do the ground wire fix in the passenger side rear.

Anyone have any ideas what might be causing this problem and where I should begin? :scratchinghead

[Hornung418]

Did you switch the bulbs from side to side with the known defective one?

From a GS3, this was sent.

[Torxuvin]

Can you trace the cable back? Maybe it's loose somewhere. Do they have different fuses?

[brettbimmer]

Did you switch the bulbs from side to side with the known defective one?

From a GS3, this was sent.

Thanks Justin. Well, old bulb that was removed appeared to be intact, but I tossed it anyway. New bulb is in a two-pack of H7's and looks good, but I have not swapped sides as the bulb housing is for people with midget hands with the Xenons next door. I wish they were as easy to work with as the E36!


Can you trace the cable back? Maybe it's loose somewhere. Do they have different fuses?

I suppose that's possible that it could be a loose wire connection, but I would be really surprised if this was the issue. Doubt that wire chafe would be a culprit here either given the mileage. Have yet to dive into the fuses, but that may be next. Bentley manual for bedtime reading...

[danewilson77]

Like J said, swap bulbs and ballasts/ignitor side to side. Beyond that it would be in the wiring.

Sent from Williamsburg, VA USA

[Hornung418]

Any rodents that would hole up for winter?

From a GS3, this was sent.

[brettbimmer]

Thank you all for the ideas and feedback. I went one further with this, and powered up the old bulb which I had removed off of a 12 volt power source in the garage. Turns out that the old bulb was good after all. Anyway, I pulled the plug off the back of the new H7 in the car, added some dielectric grease, and have reinstalled it. Seems to be working for the time being. I am still suspicious that somehow with the tail light ground recall (not yet having been corrected) that this is causing a ground-related fault in the system, as I occasionally see the check control display the right rear light out for a few seconds when I first start the car. This is not every time, but maybe about 25% of the time. Otherwise it may be related to the bulb monitoring system in general - also known as the old check control system. Perhaps it thinks that the bulb is getting too hot and is shutting it down. Wouldn't want to see any burnt bowls...:shift

Maybe this just means I just need to drive really fast all the time. Officer: "Son, DO you know how fast you were going?" :foottap Me: "Yes Officer, just fast enough to keep the lights on in my ZHP!" :swiss :ninja

DW - Is there a ballast for the inner halogens? I know that we have them for the Xenons, but want to be 100%.

[danewilson77]

Not sure Brett. I'd have to look on realoem.

Sent from Williamsburg, VA USA

[brettbimmer]

Not sure Brett. I'd have to look on realoem.

Sent from Williamsburg, VA USA

Thanks DW, I read through the exploded parts views of the lights in the Bentley Manual and didn't see anything, but I thought that maybe you had had them apart in the past. I can check Realoem.

[jack.chris328]

There would be no ballast or ignitor for a halogen bulb. You can simply apply 12V to it and it will light up. Unless you had switched to a Xenon "H7 style" bulb. Then there would be. But then it wouldn't be halogen.

Edit - Just though of this. Try checking out the bulb holder. I have seen the connections inside the bulb holder get burnt and then not function properly. You could try swapping that from left to right also and see if the problem follows. That is, if you didn't notice any when you added the grease.

[ryankokesh]

Jack sounds like he knows what he's doing. I'd listen to him.

All I know is no ballast for halogens. :dunno

[brettbimmer]

There would be no ballast or ignitor for a halogen bulb. You can simply apply 12V to it and it will light up. Unless you had switched to a Xenon "H7 style" bulb. Then there would be. But then it wouldn't be halogen.

Edit - Just though of this. Try checking out the bulb holder. I have seen the connections inside the bulb holder get burnt and then not function properly. You could try swapping that from left to right also and see if the problem follows. That is, if you didn't notice any when you added the grease.

Thank you for the info! I didn't think that there was a ballast for the Halogens - only for the Xenons. Yes, 12V power source lit up the "old" H7 perfectly.

Bulb holder & corresponding female spade plugs looked to be 100% intact without any evidence of burning or melting, but thanks for the ideas! So far lately the light has been working fine, but I have not driven the car at night much since where I have been able to really test it all out again. It was working great in the garage the other evening for about 15 minutes, but so far untested on the road.