Skip the auto shop - Our mechanics make house calls

Q: Why does the AC stop cooling the car once the car speed exceeds about 80 Km/h?

asked by on

Why does the AC stop cooling the car once the car speed exceeds about 80 Km/h? It starts cooling again at car speeds 50-60Km or lower.

My car has 60000 miles.
My car has an automatic transmission.

The A/C thermal expansion valve (TXV) most likely is the cause of the A/C system freezing up at higher engine or vehicle speeds. The TXV controls the flow of refrigerant through the evaporator and the valve can stick open causing the system to not get cold after it opens or the valve will stick on an almost closed position and cause the orifice to freeze up and cannot control the correct amount of refrigerant flow through the evaporator. The A/C system should be performance tested and checked for pressures to make sure the system has enough refrigerant or the TXV is the cause of the problems. The TXV is mounted to the evaporator and can be replaced separate from the evaporator. If you would like to have this inspected, a certified technician from YourMechanic can come to your car’s location to diagnose the AC issue in person and pinpoint needed repairs.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  • Home
  • Questions
  • Why does the AC stop cooling the car once the car speed exceeds about 80 Km/h?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Inside door handle not working

With the inside door handle not working, the most likely cause is the linkage that runs between the door lock actuator and door handle. A qualified technician, like one from YourMechanic, will be able to diagnose your door problem and...

Q: Heater blows cold air

Hello. If the A/C won’t blow cold air, this is usually due to: Lack of refrigerant in the A/C system A/C compressor has stopped working Blockage in the A/C system It will first be necessary to...

Q: Coolant reservoir is a block of ice, is it possible to thaw it out and flush the system without damaging anything?

If you have a frozen overflow coolant bottle then the same coolant mix is in the engine and may also be frozen in the engine and radiator. You will need to move the vehicle into a building that is above...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...