Further to my call for help re electrics....i have since discovered that my heated rear screen DOES work - just not when headlights (side or mainbeam) are on! a tad annoying. any ideas?

Also, im wondering if this may be because of some 'amateur' tampering in the past. i say this because in the warning set of lights on the dash, there is a choke symbol instead of glow plugs. it lights up fine and goes out all ok, but has the panel been changed at some point?

Its a 1991 200Tdi by the way...

Pretty sure they all show a choke symbol as apposed to a glow plug light, No idea on the heated rear screen though.

Can you check the switched live to the relay. The warning panel sign is the standard one (do a Google).