Stuck thermostat, clogged radiator.
Low coolant? Cooling fan not working? Defective water pump? System airbound? Thermostat not opening? Hoses collapsing under pressure Radiator plugged or flow restricted? Defective radiator cap?
Low coolant Water pump not working properly Cooling fan not working Thermostat not opening fully Radiator plugged or dirty Check the radiator fan.
Low coolant? Cooling fan not working?
Blockage in the cooling system No or little fluid in the cooling system Radiator fan not working
The radiator cooling fan is most likely not working.
Cooling fan not working, or your cooling system needs a complete service. The cooling fan should be on continuously when the A/C is on.
If coolant is up to proper level and cooling fans are working - should not overheat
Evidently the cooling fan is not working.
It sounds like your cooling is not working when you turn on the a/c system...........
A 1991 Subaru Impreza might overheat because of a leaking cooling system or because of a damaged thermostat. You might also have a damaged or leaking radiator or a cooling fan that is not working.
Type your answer here... your cooling may be not working and you might have a partially plugged radiator