AC only cools at night

[adrianaa03]

I posted a couple weeks ago that my ac was only blowing air but not cooling. Well now I'v noticed that it has started cooling again (not super cold but cool enough) but only in the late evening and at night. During the day (when it is really hot) it will not cool at all...it just blows air. The fan seems to be working fan and it does not need freon. Anyone know what the problem might be?

Thanks,
Adriana

[Davescort97]

If it doesn't need freon the only thing that it could be is that the fins on the condenser in front of the radiator are mashed together or clogged up with bugs. With the AC on open hood and spray the condenser with water. If the AC cools down that is the problem.

[Paul78zephyr]

During the day, when the AC is not working, verify if the AC compressor is turning or not. The AC compressor is mounted on the front of the engine (passenger side) and is near the front of the car and mounted very low. If you look down with the engine off you can see the compressor with the serpentine belt on it. The compressor clutch pulley has three large bolts sticking out of it. With the car running and the AC on the pulley (compresser clutch energized) should be turning (you can tell because the part with the three bolts is spinning). Check that first.

Paul

[misafasheti]

I'm sure that the original user of this thread already resolved the issue but here is what I think the answer is:
My car AC works very well in the morning, late evening, and at night. No issues there. But...during the middle of the day (Tucson AZ summers) the compressor will just stop working. At first the temperature gauge on my dashboard wasn't working but once I got it working I noticed that my car is running hot during the day, and that this is tied directly to your car AC. When the temperature needle on my instrument panel gets above halfway (up to halfway is probably normal operating termperature) then the the AC compressor shuts off and I feel warm air almost immediately. This happens more in stop-and-go traffic. Once I start to go down the road for a little while and I notice that the temperature needle moves at or below the halfway point then the AC compressor kicks back on and I can feel the super cold air again (relief!). I did some research and learned that car AC compressors have a temperature safety switch (might not be called that on all cars) that shuts the compressor down when the engine gets too hot in order to prevent self-destruction.
So my diagnosis is...faulty car cooling system. There are several things that I am going to try, as my car is old. I am first going to replace the radiator cap and the thermostat. Might as well do a coolant flush while I'm at it (all inexpensive repairs). And first and foremost make sure your car has enought coolant for the car! If that doesn't work to keep the engine below operating temperature then I'm going to pull the radiator out and have it pressure and flow tested. If it passes then at that point I wont know what else to do other than replace the radiator. A leaking water pump could also cause the issue. Another issue could be the fans on the radiator. The fans on my car have two speeds. When the car gets really hot the high speed kicks in ( I have seen it). If the fans are not spinning at their proper speed and thus not keeping the car cool enough then this could be the culprit to the overheating issue.

In short, the problem isnt with the AC, its with the car coolant system. The AC doesn't work during the day when it's hottest in order to preserve itself and the car engine. Make sure the car is functioning at normal operating termperatures.

[zzyzzx2]

Originally Posted by misafasheti

When the temperature needle on my instrument panel gets above halfway (up to halfway is probably normal operating termperature)

Actually this is normal operating temperature warmed up: