Electrical system 'pulsing'

[H.7]

I recently bought a 54-plate S4 Avant 4.2 V8. I've known the car for a couple of years and had driven it a few times before I bought it. I had noticed a 'pulsing' of the electrical system, visible as a flicker on the dash display and particularly with the reversing and stop lights when reversing into a parking space in a dark garage. It's not so noticeable on the dipped headlights, possibly because they're HIDs but, as I'm now driving more in the dark as the nights draw in, it's very noticeable on main beam (which will be halogen) and exhibits a slight stroboscopic effect which is mildly distracting.

Any thoughts as to what this could be? If it helps, previous owner says he thought it started when the alternator got wet once. Charging is OK so there's nothing fundamentally wrong with the alternator, but maybe a voltage regulator somewhere?

Thanks in advance,
Brian

[PetrolDave]

Is it the whole electrical system or just the dash illumination and bulbs?

BTW the voltage regulator has been built-in to the alternator for many years.

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Battery could be faulty causing the alternator to get a bit confused.
Could also be a faulty earth mounting somewhere.

[H.7]

Is it the whole electrical system or just the dash illumination and bulbs?

BTW the voltage regulator has been built-in to the alternator for many years.

Thanks. It's only noticeable with the lights and dash illumination. Your comment about the voltage regulator, coupled with the knowledge that it's been wet (not sure now, or to what extent), would lead me to suspect that.

[H.7]

Battery could be faulty causing the alternator to get a bit confused.
Could also be a faulty earth mounting somewhere.

Thanks. I'll check the earths. If the battery was faulty, I'd expect that to show when trying to start the car, especially after a period of not running it, but I may as well have that checked out too.

[adsgreen]

Battery could be faulty causing the alternator to get a bit confused.
Could also be a faulty earth mounting somewhere.

Thanks. I'll check the earths. If the battery was faulty, I'd expect that to show when trying to start the car, especially after a period of not running it, but I may as well have that checked out too.

Batteries can be weird sometimes - it might be something like one of the cells fluctuating causing the pulsing but the other celss have plenty of juice to fire up the car.