Q: Air conditioning works, but during longer trips it becomes weaker and weaker.

asked by on

On longer trips, the air conditioning will begin to not keep the car cool, and I'll need to turn the fan higher and higher until I'm at max A/C. Once max A/C will no longer keep the car cool, I'll turn the A/C off, roll down the windows, and after a while, the A/C will be "recharged" and will again begin to push out cool air. Any idea what the problem is? Thanks!
My car has an automatic transmission.

First thing to do is check the refrigerant charge level, typically via gauge (high and low) pressures, although note that gauge pressures do not perfectly coincide with what is intended to be the factory specified amount of charge (measured very precisely in ounces, indeed tenths of an ounce) of R134a.

Gauge pressures will tell you if the system is clearly low, as well as give you an overall indication of the function of compressor (e.g. the compressor is "compressing"). If charge is good (e.g. if pressures are within acceptable range and STABLE), you want to check and make sure the condenser is not blocked with debris or has lots of bent fins. You want to be sure that the condenser fan works, as well as radiator fan, which also draws air over condenser.

Intermittent cooling can sometimes be caused by excess moisture in the system. The moisture can freeze in the expansion valve blocking flow of refrigerant. If your system has not been opened though, there is no reason for moisture to have gotten in except in a circumstance where refrigerant level in your system has gotten so low that the low side has drawn a vacuum and air has leaked in. At any rate, check gauge pressures first. If you would like to have this checked, a certified professional from YourMechanic can come to your car’s location to inspect the AC and let you know what needs to be done.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 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!
  1. Home
  2. Questions
  3. Air conditioning works, but during longer trips it becomes weaker and weaker.

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: How do I turn off my Lexus RX330 airbag

Hi there. There is currently no legal method to disable the airbag system in your vehicle. I understand the situation with the recalls being broadcast via the news and social media. However, the manufacturers are all working on the concern...

Q: Should I have concerns on a check engine light flashing for 2 seconds just after startup and acceleration?

Hi there. What code/codes are stored in the ECM? Weak ignition coil/coils, oil saturated spark plug wires, worn spark plugs, weak/broken ignition coil electrical connectors (very common on the Toyota/Lexus straight 6 cylinder engines), cracked/split intake hose chamber (also common),...

Q: Engine misfiring - 2003 Santro Xing

Hey there. The problem with a misfire is going to involve the spark plugs or spark getting to the plugs. If the engine has no spark problems, then a fuel-related issue may be you got water in the fuel or...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
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...