81 240D Electrical Issues
 

Whenever the brake pedal is pressed, the high beams engaged, the turn signals activated & the hazard switch pressed, a popping sounds through the speakers, occasionally, at starting, there is no electrical power whatsoever, but when i open & close the hood everything is fine, cheked all the cables & ground from the battery & all check out...loose ground, relay, voltage regulator?...annoying.

Don't think it's the voltage regulator, a loose ground maybe?

Your car is CRAZY !!!
LOL,
Usually on this type thing it is best to just start at the ground wire system.... then check to see what is on the same part of the electrical " tree" ... sharing power or grounds...

x3.
I have found grounding issues to be the first place to look for wierd electrical problems. It is worth the time and contortions to check it out.
My Chev plow truck would drain the battery, cause the plow to operate intermittently etc.
Salt had totally eaten away the grounds.
Replaced them and all was new again.

checked the alternator today, only pulling 12-13v, so something is definitely loose, just trying to decide where to begin.