How cold should my AC be at the vent in my car?

The do a performance test and know how cold should the the a/c be at the vent in your car, you should follow the manufacturer specifications. The ambient air temperature must be at least 16°C (60°F) .

Do not induce additional air flow across the front of the vehicle during the test.

What temperature should the A/C blow ? 

The A/C system is designed to provide the passenger compartment with low temperature and low humidity air. During periods of high heat and humidity, an A/C system will be more effective in the Recirculation mode (MAX-A/C).

We could easily know what should the A/C temperature be at the vents be checking this manufacturer chart. Taking into account  50-60 % relative humidity and an ambient air temperature of 77 F,86 F,95 F ,the discharge air temperature at the center vent should be in the range of :

50-54 F

56-60 F

63-70 F

if the A/C system in the car is working properly.

How cold should my AC be at the vent in my car?

A performance test is the best way to determine whether the system is performing up to design standards. This test also provides valuable clues as to the possible cause of trouble with the A/C system.

How do I check the temperature of my car AC?

Testing must be performed as follows:

TEST READING

Recirculating-to-discharge Air Temperature Table

***This values are for NISSAN-DATSUN Maxima V6 3.5L***