hi it could be your heater matrix probe sensor,it checks the temperature in the matrix could be reading incorrectly its fitted on the drivers side in the centre of heater matrix just twists in and out,small 2 pin connector on it from memory think its black,the only other sensor is the heater coolant sensor this is fitted to a pipe by a spring clip and is blue in color both are on the drivers side you will have to drop the panel under steering wheel and move the side cheek on the gearbox tunnel,its easier to see them then,i would go for the heater core sensor probe first as this 1 normally efects the air con,i hope this helps tiga
