I'm in the dark about my headlight failure

[Bill_Walker]

My '04 1150RT developed a problem with the headlights in Torrey that I haven't been able to diagnose yet.

 

Neither the high beam nor low beam headlight works. The high beam indicator is on. Neither of the bulbs is burned out, nor are the fuses blown. Has anybody seen a problem like this before? In Torrey, Mikko looked at it and suggested a ground problem. I haven't had a chance to get all the t-ware off to investigate that, though I may get started on it today (if I can tear myself away from the board!).

 

I was figuring the problem was due to my Motofx BIGDO garage door opener, which is connected to the low and high beam circuits and uses them to trigger the opener. But I disconnected the module from the wiring harness and the problem is still there. It could of course be a problem in the harness. BTW, the opener wasn't seeing signals from the high and low beam, either.

 

Where are the headlight grounds connected?

[DavidEBSmith]

How did you connect the garage door opener to the headlight circuits? Scotch-Lok connectors? Those can cause the wire to break inside the insulation.

[ShovelStrokeEd]

The grounds for the headlights almost always fail right where the connect to the bulb sockets. One puny little copper spade sticking out. It either breaks off or fails from overheating due to a high resistance short created at the junction with the female spade connector. Works OK on little loads like a marker light or a directional signal. Horrible idea on headlights.

 

If it turns out to be the case, solder some copper braid to the ground plane and then work it down to some heavy sized wire (12 gauge) thence to a good lug connector and finally to a good (no paint) chassis ground.

[Ken H.]

Have you checked any voltages anywhere yet? If so, do you have voltage at the sockets?

 

The load relief relay is one thing that these have in common.

[Boffin]

I am with Ed on this one. The ground tag failure is a common problem that gives exactly the symptoms you describe - the current trys to find ground via the high-beam indicator which light is up. This is a much higher resistance bulb and drops almost all the voltage so the headlights do not light. To check it out just run a ground to the back of the low-beam lampholder and if things start to work you have found the problem

 

Andy

[Bill_Walker]

How did you connect the garage door opener to the headlight circuits? Scotch-Lok connectors? Those can cause the wire to break inside the insulation.

 

No. I cut the wires and used crimp-on butt connectors. These could, of course, be the problem. Time to do some probing with the multimeter.

 

Thanks everybody for your tips!

[Bill_Walker]

OK. I pulled the socket off the low beam bulb, and there's 12.8 volts across the terminals with the key on.

 

I pulled the bulb, and it measures 0.4 Ohms of resistance. I checked it against a spare, which measured the same.

 

If I disconnect _either_ the high beam bulb or the the low beam bulb, while leaving the other connected, the high beam indicator light doesn't come on. Unfortunately, neither do either of the headlight bulbs.

 

I tried connecting the low beam bulb to its harness while I had it out of the housing, in case the housing was providing a path to ground. No light.

 

So, Ed, are you suggesting that the spade terminals aren't making good contact with the bulb? How would I determine if that's the case?

 

Any other ideas? Things I should check?

 

Thanks for your help!

[Bill_Walker]

I am with Ed on this one. The ground tag failure is a common problem that gives exactly the symptoms you describe - the current trys to find ground via the high-beam indicator which light is up. This is a much higher resistance bulb and drops almost all the voltage so the headlights do not light. To check it out just run a ground to the back of the low-beam lampholder and if things start to work you have found the problem

 

Andy

 

Andy, I'm not quite sure I understand where I would connect this. There's a two-pole connector with two female spade terminals in it that connects directly to the low-beam bulb. Should I jumper from the positive terminal of this connector to the bulb, and then connect a separate ground wire? I think that's what you're telling me to do.

[Bill_Walker]

Well, I'm closing in on it. I've got 2k Ohms between the ground terminal for the low beam and battery ground. A bit high, no? That's one heck of a resistant wire! Now I've just gotta find out where the problem is.

 

Oh, I almost forgot to mention: I tried the above test, jumpering from the negative terminal of the bulb to battery ground. Guess what? The low beam works. Unfortunately, there's not a good way to bypass the ground for the high beam, that I can see. But ultimately they're both grounded through the same wire.

[ShovelStrokeEd]

OK, I looked at some schematics I had buried on my hard disk.

 

The brown wire is the ground from either socket. It connects, within the harness by a solder joint and goes directly to the battery ground. The wire size at the battery connection is 2.5 mm. The wires leading from the bulb sockets into the harness are 1.0 mm.

 

My best guess would be that the bulb sockets have failed. The good news is that you can buy new ones at just about any automotive store. I'm a little suspicious that both failed at once though. Might be trouble within the harness.

 

Looking at the power side of this for a minute, power comes direct from the load shed relay, through the left side switch gear (hi/lo) and thence directly out to the lighting harness. There are a couple of potential failure points there as well, starting with the load shed relay, its socket, the connector to the left switch gear, the switch gear itself and finally, the bulb sockets.

 

Don't let the voltmeter fool you in this situation. You may see the 12 volts on the meter but, add a load and it could drop to nothing. Bulb sockets are dirt cheap at the NAPA store, bring a bulb to match the connections. Cut out the old ones and splice in the new.

[Bill_Walker]

Well, I pulled the nose off so I could see what was going on. Measured essentially zero resistance from the chassis side of the harness connector to the battery, and (much to my surprise) 0 ohms from the nosepiece harness connector to the low beam connector. Huh? OK, so there must not be a good connection in the connector, right? So I cleaned both sides of the connector, dried it out, plugged it back in, and voila! I said, voila! VOILA, DAMMIT!!! Nope, no lights.

 

So, I hunted around some more. I started tracing where the ground wires in the nose went. The ground wire from the harness comes in, connects (with a spade connector, of course) to a metal plate on the underside of the housing. Presumably, this plate provides the ground connection for the high beam bulb. There's another spade connector on the plate, and wire from it runs to the low beam bulb connector. But wait! Something doesn't look right here:

 

One of those spade connectors (the one that's _not_ in focus, of course) looks suspiciously black. I tried to further disassemble the housing to get a better look at it, but the lens is sealed with some RTV or something and I didn't want to mess with it. So, I cut the offending connector off. It looked like this:

 

I neglected to take a picture before I cut it off. So, I slapped a new spade on there, connected it up, and voila! Yep, really voila! this time. The lights work.

 

Of course, I've probably only treated the symptom. What caused that connector to burn up like that, and how long will it be before it happens again? Any ideas?

 

So, maybe I'm going to have open that sucker up after all.

 

Thanks for your help, gentlemen!

[Boffin]

I am glad you got there. The failure you have is the one I was thinking of. In my first post I meant for you to put a temporary ground to the metal surround of the lamp - that is where your burnt connector goes to eventually.

 

The reason for the failure is, once again, poor design. That type of spade connector is rated at 15 amps max. But that is a peak rating, for continuous use it should be de-rated to closer to 10 amps. With high-beam on the headlight has 2x55watt lamps, running at 14v, which is 110/14 = 9 amps, so all looks just dandy but it isn't because the connectors rating assumes good clean joints with high pressure on the contacts. If you get a slightly loose connector, or a bit of corrosion in there the connector starts to get hot. As this heat increases so does the corrosion - the blackening you see - and the joint resistance goes up making it get hotter. This leads to the connector burning out. This frequently burns out the connector moulded onto the headlamp housing which then either needs replacing or a better, higher rated, connector being somehow attached.

 

The lamp makers use one of these connectors per lamp. BMW share two lamps to the connector. If BMW had not also under-specified the wiring harness leading to lower current draw overall then we would see many more of these failing.

 

Andy

[Ken H.]

What caused that connector to burn up like that, and how long will it be before it happens again? Any ideas?

Failures like this are often a bit of a cascade effect. As mentioned, it starts with a poor design to begin with. Then a bit of corrosion starts to build over time and vibration between the spade male and female part of the connecting point and the resistance there goes up. This produces more heat at that point, which accelerates the corrosion. And the connection point gets even more resistance and starts to cook the wire. Which loosens up some, more resistance, more heat. When it progresses far enough, total failure.

 

Tight clean connectors, soldered wire to the space lug, use of dialectic grease, all can help starve off a repeat.

[smiller]

use of dialectic grease

Oh no, don't start that one up again..!

[ShovelStrokeEd]

Take that very ground wire, on which you replaced the connector and splice it directly into the brown wires coming off your two bulb sockets. That way you bypass that silly ground plane altogether. If you wish, you can leave it on there as well. Won't hurt a thing.

[Bill_Walker]

Take that very ground wire, on which you replaced the connector and splice it directly into the brown wires coming off your two bulb sockets. That way you bypass that silly ground plane altogether. If you wish, you can leave it on there as well. Won't hurt a thing.

 

Thanks, Ed, I'll look into doing that. Though I think from my examination so far (and without checking the manual or parts fiche) that that ground plane is the only ground connection for the high beam bulb. But I can certainly splice in the connection for the low beam bulb, which is the one that's on all the time anyway.

 

Thanks also to Andy and Ken!

[stager]

Sounds like the ground tab on the headlight assembly. You may still get a dealer to cover it under warranty. It's a problem that has occurred on a number of 04 RT's.