I have a 93 honda civic 4 dr,and the car over heats when the heating air vent is not on it over heat it has A/C could this be the issue

 

The manual that comes with cars usually reccomends turning the heat on when a car starts to over heat. I could be low coolant, air bubbles, bad head gasket, bad water pump, thermostat, or a leak.

 

Thanks i will investigate

 

Check to see if ur radiator fluid looks milky brownish...if so then it could be a head gasket problem....

 

i recomend chaning the auxilary fan switch this solved the overheating problem on my 92'civic si after i changed the thermosdat, rad cap, ect.

 

questions:
a: is the fan coming on, if not then your thermo switch is bad.
b: is the lower radiator hose hot after the car warms up...if it is not, then your thermostat is stuck closed.
c: how many miles are on this car, and when is the last time the thermostat was changed?
d: how does the radiator itself look, is there any buildup, excessive bent fins, bent or crimped coolant passages?

 

The A/C can cause your car to overheat if you are idling for a long time or going up hills