My furnace keeps blowing fuses why it is a nordine model #e2eb-015ha

The first thing i would do is shut off all the power to the unit and disconnect all the wiring from the thermostat. then i would install a jumper wire from R to W on the circuit board and see if the furnace runs good. if it runs good and does not blow a fuse, your problem is in the wiring between the t-stat and the furnace. If this does not help, please indicate if your system is a straight a/c, furnace system. or if it is installed with a heat pump. also does it make any difference what the temperature is outside. for example, does the fuse only blow when the temp drops down into the 30s or does it not make any difference.