help please emmisions and warning light come on ,drains battery. golf mk 4 ?

Emmsions warning and engine symbol light has come on my 2002 1.6 golf ?
hi i am having trouble with my very recently bought Mk 4 golf 2002 1.6 SE .The emmisions warning light flashes up and the amber engine slight comes on my battery also ran flat .The fans seem to work for a long time after I have switched off but stop when I start engine .So far the RAC gave me a sensor check and a code and a reset and the main VW dealer I bought from fitted a new sensor .Its still happening and sometimes draining the battery .The temp gauge doesnt work correctly .sometimes when I wiggle the wires around the sensor it all corrects itself except the temp gauge .The engine l warning light goes out as well.any ideas would be gratefully accepted and give me some ammo when I take it back to the dealer .The car is genuine low milage and has full VW main dealer service history .

martin
November 2010