I fix the thermostat on my 2002 Grand Am and now my heat don't work
Your engine may be air locked. Did you fill the engine back up to the thermostat level before installing. If not find the bleed valve on the coolant system and try to bleed the air out of the motor. Always fill the coolant system through the rad. The reservoir is only for topping up a functional system (if the rad or engine are low on fluid they cannot draw fluid from the the reservoir). Once the air lock is fixed in the engine the pump will be able to draw coolant through the heater core. Caution do not run the engine for long periods as it will get very hot.