Mercedes C220 CDI - electrics and servicing

Hi folks

I have a 2002 Merc C220 CDI. Two questions (perhaps for people who are familiar with the model?)

- does anyone else have problems with the electrics? Seems to be an ongoing thing for me. Latest prob this week is the windows get stuck - was afriad I wouldn't be able to close it in a gale wind last week when thankfully it finally moved! The radio panel also gets dimmer or brighter occasionally. Had a problem with the regulator when I first got it in 2007, but it was under a one-year used car warranty so got it fixed. My repair guy, who only does Mercs, can't seem to find the problem

- how often would you recommend a service? Since it's a 2.1 diesel the tax is a killer for me at over €800 a year :eek: so I want to try to trim other costs for it where I can. Was normally getting it done twice a year, do an avg mileage of about 18,000 a year, last had a full service in August.

Thanks for all advice!