Hi all,
This one has me a bit flummoxed at the moment...
The car is a friend's Passat 1.8T 1998 (I think).
There is a pretty-much constant buzzing noise coming from the Hazard light switch and from the stereo speakers if it's on. It's related to engine speed - maybe one click per rev or so and is accompanied by a very faint glow from the battery warning light. The hazard switch buzz seems to be an effect rather than a cause because using the indicators stops it happening, but the battery light and stereo buzz remain. Seemed like an obvious alternator fault, but he says he's run it with the alternator unplugged and the problem stayed! The only other explanation I can think of is that something is very heavily but briefly loading it's power supply and causing loads of noise on it. I'll lend him a scope to check at the cigar-lighter tomorrow but, assuming the noise is there, what could be causing it? To be engine speed related, it must be an engine actuator or something, but the car still seems to run fine. Maybe some emission control valve or something?
Any ideas,
Colin.