Car heater just defrost work

When you set the control, if you chose defrost, it usually does it at the temperature you specify. So if you want heat only blowing through the windshield vents, which I believe may be the question you are asking, it varies between makes of cars.

This is what to look for : defrost, fan speed, temperature.

If you mean "Can a car that only has a heater ( no air conditioning ) be used to defrost?" The answer is still yes.

I believe the question is missing Words. It is comparable to asking "Hand, just finger work?" You might try asking again, being more specific, explaining why it is a problem.