Flickering lights on my 325is

[nukeduster]

Well, Ive seen this posted countless times and never seen an actual fix before so I figured I'd post it again for all to see and see if fresh eyes can find a fix.


My 1992 325is's lights (all of them) flicker quickly when the engine is running. Its a pulsing or throbbing that all the lights experience.. backlights of the gauge cluster, obc, interior lights, headlights, brake lights, tail lights, etc..

the flickering is going on at any speed, and doesnt appear speed sensitive.. @idle or cruising in any gear.

Ive seen this problem alot and people try replacing batteries, alternators and neither fixed the issue for them. They never follow up though with how/if they did fix it after trying those though.

One thing: the lights all work normal when the engine is NOT running but running solely on the battery. Dont appear dim or anything, just normal..

[Gator]

The only thing I can think off that might cause the problem is a bad ground connection. Check and clean the ground wire on the battery and where it connects to the chassis. For the chassis connection you really need to disconnect it in order to be able to see the corrosion on the underside of the terminal.

[nukeduster]

Actually I have another theory, ive only seen this problem exhibited on 92 and 93 bmws before and lo-and-behold, i checked out the wiring diagrams of the charging systems of all the year bmws and 92 and 93 had the same charging system and they changed it in 94 and beyond.

aparently they added an uncoupling diode to the climate control module that is supposed to prevent the a/c of the alternator from fucx0ring with the rest of the d/c system by having interference.

thus is my theory at least, ill test it when i get home from vacation next week or so.

if it doesnt work ill just put a .25 farad cap inline with my headlights so they dont pulse witht he rest of the lighting system so at least they'll be safe even if the problem cant be solved.

but im pretty sure thats the problem as its the main change that bmw did to the charging system from 93 to 94, and 94's and later never seem to exhibit the problem.