I've searched the threads but don't think I've found the answer...Hope someone can help.

I have OEM dealer installed Voltage and Oil temp gauges in my '04 R53 (17 years ago).
Recently, I've been having this strange voltage drain reading from the volt gauge every time I turn on my lower driving/fog lamps.The voltage drops down to 0, the oil temp pegs out to 150° C and gauge light go dim.
Turn the driving lights off and voltage goes back up to 13.5 - 14 volts as does the oil temp. All goes back to normal. The car always runs fine.

More weirdness; Even with all exterior lights off - If I turn on the AC, as normal, the voltage drops from 14 to 13.2 volts...That is - Until the cooling fan kicks on - then the same thing happens = voltage gauge drops to 0 and oil temp gauge pegs,The volt gauge light goes dim and oddly enough the lower driving lights (for some strange reason) glow, as well as the upper left side turn signal light also glows dimly.
Both of these odd voltage drains occur with the headlights and driving lights off. So there is no additional power being drawn.

The Battery has been replaced. The anomaly persists even with a brand new battery.
The the local auto parts store will not test my battery when the car is running since it is "against their policy" to go inside a customer's car (understandably - battery is in the boot = inside the car).
The battery indicator light on the speedometer never lights up when this happens.The alternator was replaced by the dealer about 8 years ago. Low and high speed fan work as normal. But cause gauges to go wonky.

I've checked/cleaned all the grounds that I could find/access and battery terminals are clean.

I don't know much about resistors so I have no idea if that could be related.

Any Ideas would be appreciated.

 

I'm suggesting that somewhere, in the driving lights and cooling fan wiring, you have wires that are exposed and crossed up, causing a short circuit. They're probably pinched together and chafed. Fortunately, the Voltage gauge is telling you something is wrong. You may need to put the front end into "service mode" so that you can properly access, trace and inspect the wiring.

 

+1 on TrackRat -- you have a wire that's shorting out when power is applied. Trace the wire(s) from your driving lights back to the switch. You'll more than likely find a frayed wire touching metal somewhere.

 

Thank both of you for your quick response!
It wasn't until Trackrat brought up "putting the car into front end service mode" that it dawned on me...
"Recently" may have been an exaggeration on my part. The problem actually began 3 years ago. I now remember - I brought the Mini in to an independent BMW garage for a clutch replacement.
The mechanic told me he had the car in front end service mode. Since it was in the Fall, I never noticed the issue until a few weeks later when it began getting darker in the early morning hours on my way to work, when I turned on my driving lights.
It wasn't until late Spring when the weather was warmer and started using the AC that I noticed the same issue. I am not citing blame. It just seems coincidental.

Your advise makes perfect sense. I'm going to try and do it this weekend....(after I try to fix my door lock issue)

 

OK - Before doing anything; This morning I tested the aforementioned problems independently: Lower driving light voltage drain and AC / cooling fan voltage drain. Both problems were still present.

Following NC Trackrat & cooper48 recommendation; I took off the front bumper cladding before going all out, into front end service mode. Just to see if I could spot anything obvious starting from the lights themselves.
I traced the wiring from lights to harness in the engine bay. Nothing appeared frayed or pinched. Then I noticed this:

Can anyone tell me what the heck this is?......


Located left (driver side) just underneath the hood latch cable. Circled in red : is a thin, black, ceramic(?) "plate" or"ballast" with wires embedded in it leading to/from the wire harness.
There is a bolt and nut securing it in place... the nut was missing.

A wild guess, perhaps,, but It appeared to me that this wired "ballast/plate" is intended to be grounded. I replaced the missing 10mm nut and re-tried turning on the driving lights....
BAM! = absolutely no voltage drop/drain. Volt gauge shows; charging just under 14V
Ran the AC, the slow, then high speed fan kicked in - need I say; no voltage drain . Voltage fluctuates between 12.2.& 13V .
Under load / Everything turned on, running at idle: running lights, driving lights, headlights, rally lights, AC blowing cold, high speed fan winding up = 12 - 12.4V
It maybe a fluke. Or it maybe turning out to be a good day after all (?)

I'm hoping this may have fixed my strange voltage drain issues.
Thanx again for the great advice!

(Notwithstanding;
I never did manage to figure out my door lock problem today. I can hear the actuator fully engage (unlock) but the pull **** nor the door will unlock (works w/key only)...
But that's for another thread. Still searching the forum....)

 

Well it wasn't a fluke.
Grounding (with a missing nut) this "ballast" solved my weird voltage drain issues that have plagued my Mini for the past 3 years.
According to the Bentley Manual it is identified as the "Ground bus X175" (page ECL-19, Fig. 10 Ground Bus, left front).
Won't be bringing my Mini to that BMW garage ever again.

 

Way to go, Here2Go! We just pointed you in the right direction but you solved your own problem.