check your grounds. could be loose/corroded/open. also do a diag on the alternator. do you have to jump off the car after a few days of night driving? then could be alt. have it checked

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'81 240D -sold
'89 300E -sold
'79 300SD -no oil I-10
'86 300SDL-totalled
'91 300SE -sold
'79 300SD-
'97 E300D
'95 YOTA4WD