112cdi vito speedo problem
 

can any one help me, i have a bit of any weird problem with the speedo cluster in my 2001 112cdi vito.
Any time the air temp inside the vandrops below 10c the whole cluster flashes on and off untill temp inside cab rises above 10c.
Not much of a problem in the summer but in the winter is quite anoying. Help! not sure wether to by new clocks or if its somthing else.