AC Stops Blowing At High Speeds: Reasons And How To Fix

You anticipate your car’s air conditioning system to operate well, regardless of the season. However, AC stops blowing at high speeds might occur frequently.

If your air conditioner isn’t blowing, it’s a fairly common issue that may be resolved without taking your car to the shop.

AC Stops Blowing At High Speeds: The Reasons

ac stops blowing at high speeds

It can be aggravating if your air conditioner isn’t blowing or turning on.

Spindle issues, faulty coolant sensors, and malfunctioning AC fans are all potential causes of this issue. Let’s research this together.

Broken AC Fan

Your AC fan could be damaged if AC stops blowing cold air after a while.

When moving at high speeds, the blower fan can occasionally be forced rearward or inwards, which inhibits its motion and can cause it to slow down or stop entirely, heating the compressor function and forcing the AC to shut off.

If the fan is not running, check to determine if it is hooked to a live outlet and if any cables or connections are broken or loose.

If your electrical system is in good operating order, the most likely cause of your AC fan not functioning is an issue with the motor. You should have a careful cleaning operation.

Fan Electric

The fan’s electrical system is another potential factor for car AC stops working on highway. You can have a visual check.

Something may be coming free at high speeds and stopping the fan containing the AC.

Your breaker can trip if the system is overheated. Your AC control unit won’t function since the fan won’t keep turning.

Take good care of your breaker box. Because of the high voltage, contacting the broken wire could result in an electrical shock.

Calling a skilled electrician or HVAC technician is preferable if you don’t feel safe around your circuit breaker.

Low Refrigerant Pressure

The amount of refrigerant within your car is described using a fancy term called a refrigerant charge.

Low refrigerant pressure will cause the pressure switch to turn the AC compressor off to avoid damage.

Air conditioning leaks within the cooling system typically cause a low quantity of refrigerant.

The compressor runs the slowest when the automobile is parked because it is based on the engine’s speed.

The compressor may produce adequate and allowable pressure while the car is driving if there is a sufficient refrigerant charge to work with.

Bad Engine Thermostat

The thermostat is in charge of controlling the engine’s coolant flow. The coolant circulates inside the engine through an expansion valve until it reaches the ideal operating temperature.

Once the engine reaches the perfect working temperature, the thermostat opens to let the coolant flow through and go to the radiator. 

The radiator ensures the machine never gets too hot and always operates at the ideal temperature. A bad radiator can cause problems.

A broken thermostat may continue to run. The engine overheats once it starts to malfunction, and if the circulation issue is not fixed, it can eventually boil over.

Costly auto repairs may result from this.

Faulty Coolant Sensor

The PCM receives information from the engine coolant sensor, which is crucial because cooler engines need more fuel to produce the same power.

The coolant sensor measures temperature, identical to engine temperature, before it flows through the radiator.

However, a malfunctioning coolant sensor will give a false reading. Multiple additional engine performance problems would result from a damaged coolant temperature sensor.

Viewing real-time data on a scan tool makes confirming the temperature sensor’s functionality easy.

Failing Compressor Clutch

The refrigerant must be under the proper pressure reading for the air conditioner to work correctly.

In addition to the lack of cooling, there is an opportunity for air conditioning compressor damage when the pressure is too low.

Some vehicles, most notably the Honda City, maintain an ECM cuts-off switch that the ECU/ECM employs to prevent the AC compressor from providing the engine speed with more power during motorway overtaking maneuvers.

No need to panic if this is how your automobile has always been when you acquired it.

AC Stops Blowing At High Speeds: How To Fix

car ac stops working then starts again

Check Your TPS

Checking your TPS (Throttle position sensor) should be your first step. It detects where your throttle is located. The TPS sensor is located on a throttle body’s butterfly spindle and shaft.

Assuming you are trying to pass another vehicle or up a hill, the automotive air conditioning system will disable the AC if you push more than 70% to conserve energy for the engine.

If your TPS is not accurately detecting the location of your throttle, it will unquestionably shut off your air conditioning at typical cruising engine RPM.

My car does that when I try to floor the paddle, but when I’m in a good mood, it cools down even at more than 120 km/h.

Refrigerant Recharge

The air conditioning system in your automobile may need to be recharged if you find that it starts to break down and stops blowing cool air.

Recharging an AC involves adding coolant to the AC cooling system to blow cold air again.

It only requires to be recharged once, so if the refrigerant is needed, identifying the leak now could save you money later.

According to Freon, what an auto repair shop would charge to do this is unknown to me. R12, which was phased out in the early 1990s, R134a, which is the most prevalent but is being phased out, and this new, expensive R1234yf are all different prices plus labor.

Replace AC Relay

The AC relay gives power to the compressor clutch and plugs into a relay box that typically lies inside the engine compartment.

If this is a faulty component, and your automobile’s AC fan isn’t operating, you might need to replace it.

Replacing a bad relay is a reasonably straightforward procedure, but hiring a professional will be simpler without the right equipment and knowledge.

To find out if this caused your problem and whether you can fix it yourself, you’ll need the assistance of a skilled mechanic with a two-dial pressure gauge to replace broken components.


ac only works when driving slow

Why Is My Car AC Not Blowing At Full Speed?

There are numerous causes for the A/C not blowing cold air.

Simple reasons range from a loose electrical connection to a worn compressor, evaporator core, blocked system, bad air filter, or bad air vents.

Although there is a good chance that the engine fan switch is to blame, a faulty blower motor resistor, which regulates the voltage sent to the blower speed, is more likely to be the culprit.

Due to this, only one speed—typically the highest speed—remains usable. Depending on the temperature of the outside air, you might not always need this speed.

Why Does My Car AC Stops Blowing Air After A While?

If this car’s ac stopped blowing air, evaporator icing, which I have witnessed in two different vehicles, is one possibility.

Here is what will happen: The acceptable level of refrigerant slowly drops over the years due to a slow leak in your system.

The system continues to function for some time.

The gas can still be sufficiently compressed by the compressor clutch coil so that it condenses in the condenser, which is necessary for the system to function.

Should AC Fans Be Slow Or Fast?

The answer depends on the model. Since the air spends longer on the evaporator, the proper cooling is generally better the slower the airspeed.

The inclination is to utilize the fastest speed to acquire the maximum volume, but doing so will make the air less frigid.


Now that you are aware of the causes and fixes for an AC stops blowing at high speeds.

Modern automobile air conditioners incorporate a pressure sensor into their circuitry to prevent this problem and maintain desirable pressure levels.

After reading this essay, you can discover your answer.

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