If heater fan does not blow either cold or hot air the problem is caused by a faulty resistor unit. This unit is located on top of the blower motor housing on the passenger side of facia. To get at this, remove the glove box assembly (3 screws). Prise up edge of carpet in glove box to gain access to lower screw. When glove box assembley is removed you will be able to see blower motor. Remove screw holding unit, disconnect wiring and twist off resistor assembley (anti clockwise) . A replacement unit can be obtained from a Renault dealer. I live in Ireland and it cost 30 Euros. Probably cheaper to buy in UK. I am assuming that your laguna does not have AC as according to Haynes, on these models the unit is an integral part of motor casing and cannot be renewed seperately. Good luck
Decon
March 2006