i have a vita spa model name vintage. its a bout 15yrs old. cant get it to go above 90. have been told its probably thermostat. where can i purchase that tiem on line and are they hard to install. thxs much for your help

Your basic thermostat control can be found at http://spapartsnet.com/parts-ELB2TSTD.html
however, if you have a Printed Circuit Board you will need to replace the sensor that is on it, In order to get the right sensor you will need to provide the model #'s off of the control box.