occasionally i'm getting a fault code stating the temp is below the t.stat temp (sorry cant remember the code #). the needle goes right to the middle of gauge (or ever so slightly less than middle- cooler).

is it more likely the t.stat is bad or just sensor mis-reading the temp?

thanks in advance

 

Hard to say, I would do both. FYI, most Volvo shops customarily change out the temp sensor when doing the thermostat and vice versa.... Pricewise too they are cheap (thermostat is 13 bucls and temp sensor is like 35ish thru fcp)....