Weird Car AC Issue: AC is freezing cold when the weather is cool, but extremely hot when the weather is hot.?

Question

I have this issue for 5 years. HondaCivic 93 144k. The AC is cold when weather is cool, but blows hot air when weather is hot. Recently I brought it to a mechanic. After inspection, he said there was no leakage, the compressor works fine. He replaced the expansion valve for $250 and refilled the freon. He used a temperature measure device to show me that the air blowing out of the expansion is 33Fdegree. So I thought he fixed the problem. It's been 3 weeks; I still experience a similar issue. When I use my car around 10am to go to work, the AC is freezing cold. The AC would continue to be cold forever if I don't turn it off. When I go uphill, the AC stops blowing cold air until I get over the hill. My job is in a hot valley, the car parked outside, air in the car get up to 200F. At lunch (2 hours later), the AC can still get cold. When I drive home at 6pm, the AC blows extremely hot air. The trip takes 30'; the AC seems to never stop blowing hot air. At 8pm, it can get cold again

Thank you for your answers

Hi Jack W,
I called the guy to tell him about your solution. He said he did try it by putting only 1/2 pound of freon in, but it still didn't get cold. Then he concluded the expansion valve was broken.

Hi Fordman,
He said that for my Honda, 1 pound is the maximum he can put in.

He asked me to bring the car back. He is 80 miles from me. Are there any more recommendations so that I can try them all this time? Thanks

Answer 1

Well the up hill loss of cold air is likely a vac problem letting one of the heater / A/C doors close, or open. You should have it checked to see if there is a vacuum leak or a vacuum tank that is disconnected or even a check valve that is week. Maybe work late so you don't leave for home until 9:00? Good over time!

Answer 2

If the air was blowing out at 33 deg then there is not enough freon in the system. Then when it gets hot, your low pressure switch will cut out the compressor. Take it back to the guy and tell him you are low on freon.

Or you can go to an auto parts store and buy a refill kit for the type of freon that you have is should be r134a. Hook up the gauge and put some more in it until the gauge reads good. The air will not actually be as cold, but the compressor will keep running and therefore it will be colder in the end. I hope that makes sense. If it's too cold, it cuts off, warms up and then comes on again for a sec or two and cuts off again.

Even better take it to another mechanic and let him look at it. either way you are low on freon. good luck.

EDIT:
Sorry, I didn't read the whole question, if it cuts out when you go uphill there very well may be a vacuum problem and that will mess with the blend door. I still think the 33 deg is too cold . One way to check is to take a short jumper wire and unplug the plug for the low pressure switch and jumper it out. Take the same trip, and if the air stays on, then you can tell that it is low on freon. Just don't leave the jumper in once you determine that it is or isn't the problem. good luck.

Answer 3

I just encountered a similar problem in a 2005 Nissan Sinatra. I believe in 1993 the Honda civic came out with R134A and in either case my diagnosis would be that your system is over charged. Your system calls for 17 to 21 ounces of refrigerant. As with your Honda it gave indications of the expansion valve being stuck. In the morning when I first tested it it was getting 38 degrees out of the vent. Later that afternoon I retested it - the ambient temperature was about 97 degrees out and the best I could get was 60 degrees out of the vent. I recovered the refrigerant and recharged the system with about 2 ounces less that the manufacture specifications and was able to reduce the vent temp by almost 50 degrees. I hope this helps - good luck

Answer 4

I WOULD CHECK THE VACUUM LINES FOR ANY LEAKS OR CRACKS.

ALSO CHECK TO SEE IF ALL YOUR CONTROLS ARE WORKING CORRECTLY ESPECIALLY THE RECIRCULATING DOOR.

REFRIGERATE ON THAT VEHICLE IS 21 TO 23 OUNCES.

AND IT SHOWS THAT VEHICLE TO HAVE R-12 FREON.

YOU ALSO HAVE WHAT IS CALLED THE AMBIENT TEMPERATURE SENSOR AND A THERMOSTAT AND A COMPRESSOR CLUTCH RELAY AS WELL THAT MAY ALSO BE A PROBLEM.

AT THIS POINT IF THE VACUUM IS OKAY I WOULD.....

TRY FINDING AN INDEPENDENT SHOP INSTEAD OF THE DEALER OR A CHAIN STORE BECAUSE YOU WILL BE OVERALL MORE PLEASED WITH THE FINDINGS AND THE SERVICE.

LEAVE IT THERE WITH THEM SO THAT THEY CAN FIND THE PROBLEM FOR YOU, IT WILL BE A LOT BETTER THAN JUST REPLACING PART AFTER PART AND NOT DOING ANY GOOD.

Answer 5

i would just take it back to the man you already paid,it's up to him to fix it.