Low Beams and Fogs Out Except with High Beams On

[BMWtyro]

The title tells most of it. Low-beams and fog lamps will not come on unless high-beams are on.

-- Completely stock U.S.-spec 7/86-built 325e (use '86 ETM).

-- No wiring ever cut, no modifications beyond use of Sylvania Xtravision sealed beams and Sylvania Silverstar miniature bulbs.

-- No power to low-beams or fogs without high-beams on.

-- Fuse panel terminals 13 and 14 are dead unless high-beams are on.

-- Relays checked and high-beam relay replaced (probably needlessly).

-- Low-beam headlamp bulbs replaced.

-- Headlamp switch replaced.

-- Dimmer switch replaced.

-- Wiring checked.

-- Tons of money and time wasted; I have been chasing this gremlin for weeks.

Now: my BMW guru suggested that the problem might be in the "Low-beam check relay" which is incorporated into the fuse panel's PC board. Before I blow more money and time on a new fuse panel, is there any way to confirm that that is the problem?

If so, is there anyone who remanufactures them so that I don't have to spend hundreds on an NOS panel?

Any other suggestions . . ?

Jeff

[tomstin]

My guess is you have a bad ground on the low beam side and you're back-feeding when the high beams are on. Make sure you have continuity to ground as you come off the switches. If you pull fuses 13 and 14, low beams on, with a test light, do you have any power to the fuses then? You have a real head scratcher on your hands!

[BMWtyro]

Tom,

No, I have no power at 13 & 14 unless the high-beams are on.

As far as the ground wires go, I have removed, wire-brushed the terminals, bead-blasted the bolt and reinstalled the cluster of four heavy-gauge brown ground wires attached to the left forward inner fender using dielectric grease as insurance. No change.

Jeff

[tomstin]

Let me try again, and I'm not trying to be a pain in the butt. Have you checked the various circuits, with a multi meter, from the switches to their termination points?

With fuse 13 & 14 fuses removed, headlights on, do you have 12 volts on one side of the fuses? Looking at the wiring diagram, I would think, that would tell you if the Low beam check circuit was working.

I know it is tedious checking all the wiring, but necessary in this case.

I'll go back in my hole...good luck!

[BMWtyro]

Tom,

No problem. I have checked all of the circuits that I can figure out how to check; the complexity of this car's electrical system leads me well outside of my comfort zone.

I have no power ACROSS fuses 13 & 14, but I will check them to ground as well when the car returns home later today. And yes, fuses 13 & 14 were verified "good" with a digital ohmmeter.

Jeff