top of page
  • Writer's pictureMarco Bonifaccino

Proper Auto AC Vent Temperature. What temperature should the AC blow?

Updated: Aug 18, 2022

How to check if the vehicle AC is cold enough? Do ambient air temperature and relative humidity affect what temperature should the air conditioning system blow?

In this video, the founder of AC diagnosis, Marco Bonifaccino, explains how the environmental conditions outside the car, ambient temperature and relative humidity, affect the performance of the car air conditioner. And how IoT (Internet of Things) technology can help the car mechanic and the car repair shop to perform a more accurate AC performance test taking into account all these parameters.


As a rule of thumb, when the ambient air temperatures 70° degrees Fahrenheit (21° Celsius) and humidity 20%, the AC outlet air temperature should be in the 35°-40° degrees Fahrenheit range. On the other extreme of 80° degrees Fahrenheit ambient air temperature and 90% humidity condition, the AC outlet air temperature might be in the 45° to 50° degrees Fahrenheit range.

That is a temperature differential of 30°-35° degrees Fahrenheit. Because of all these variations, it is difficult to pinpoint what the AC outlet air temperature should be on all applications.


For a technician testing the vent temperature during an inspection to determine if the AC is working as designed, a thermometer is typically inserted into the dash vent. However, the results are inaccurate in many cases since the vent temperature isn’t tested relative to the ambient temperature, and humidity isn’t checked at all.

For car repair shops and mobile technicians who perform AC services and repairs, today’s equipment has obvious gaps.


When customers demand timely, verifiable, and accurate diagnostics, non-disputable technology can provide the proof, precision, and expediency required. AC diagnosis integrates IoT technology to test a vehicle’s air conditioning performance at the vent, then shares a report with the findings directly to the customer’s device through an app.

What sets AC diagnosis apart from other methods?

  • The vent temperature is measured like a thermometer. However, it also measures ambient air temperature and humidity to calculate how the AC system is performing relatively, giving a much more accurate test result.

  • The sensor fits into the vent in seconds and the report takes only a few minutes to generate. Contrast that to the time it takes to perform an AC pressure test at the valves under the hood or evacuate, pressure test, and recharge an AC system, and it’s clear that AC diagnosis slashes the time it takes.

  • Results are indisputable. The customer receives a report directly, building trust in the technician and their tech.

  • Because it’s so quick, AC diagnosis can be implemented as part of any complimentary or paid vehicle inspection checklist to add authenticity and trust.

Repair shops and mobile service providers consistently strive to improve the customer experience and develop trust. That’s what creates loyal customers, and repeat business is the most profitable. Help build that trust by implementing smart AC diagnostics into your service routine with AC Diagnosis.

Visit and discover how Smart IoT technology can help you to know easily if your car's A/C is AC is cold enough!


Daniel Wickham
Daniel Wickham
Jun 14

It's crucial that the HVAC contractor uses a properly calibrated thermometer to measure the AC vent temperature accurately. This ensures that the readings are reliable and the system is functioning optimally


Feb 15, 2022

Thank you so much for sharing this information, I am sure that this information can surely be helpful for those who are looking to repair ac unit.

bottom of page