W210 E320 CDI lights lightly flashing 'beating'

[W124ali]

Hello

I have a 2000 E320 CDI. Recently the interior and exterior lights flash, ever so lightly, but noticeable. The dash lights and headlights are the ones I notice when I'm driving or stationary in traffic.
Any help would be great. Thanks

 

[bob6600]

Most likely bad earth on these, due to them being prone to corrosion. Check under the bonnet, there are some earth straps. The one behind the headlamp(s) are common.

 

[alecmascot]

If it's rhythmic it will be the alternator. If you have a MB 2.0 you can graph the 12v.

 

[Ted]

As @alecmascot says, this will either be the voltage regulator on the alternator or possibly a poor connection between alternator charging output and battery.
If the vr is easy to get at I would change this first.

 

[bob6600]

^^ Good points above, didn't think of that