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AC Problems Outlet Vent Temp Varys after about 10 mins on

seamonkeys1 on Sat April 24, 2010 11:08 PM User is offline

Year: 2005
Make: Toyota
Model: Corolla
Engine Size: 1.8
Refrigerant Type: R134A
Ambient Temp: 70
Pressure Low: 25-45
Pressure High: 135-120
Country of Origin: United States

I have a 2005 Toyota Corolla which is having problems cooling in 65-80 degree weather. If the Temp is over 85 degrees it works awesome or if the engine is idling. Here is what happening. The outlet temp varies from 43 to a few degrees cooler then what outside temp is and does this cycle over and over. I evacuated the systems and added proper amount of r134a in the system. It was missing about 1.5 oz. It was able to hold a vacuum for 30 minutes added what the service manual requested for oil and type.
I have been doing some research on this Toyota model seems to have some problems with the expansion valve. The valve is around 50 online the only problem is it is hard to replace. Does this sound like a bad expansion valve? Or a different problems. It should be up in the lower 70s this week and can give you a high pressure read out if needed then.
How do you test the expansion valve?

mk378 on Sun April 25, 2010 10:39 AM User is offline

Unless you've flushed or replaced parts of the system, oil should not be added. You probably have too much oil now. Just recovering or evacuating the refrigerant doesn't remove much if any oil.

When it is not cooling, check if the compressor is still engaged, and if it is, measure the pressures. If this problem occurs only while driving, you'd need to tape the gauges to the windshield or run the hoses through the side window to inside the car so you can watch pressures during a test drive. Have someone else drive while you observe the gauges. With an intermittent problem, tests are only meaningful if done while the problem is occurring.

seamonkeys1 on Sun April 25, 2010 12:46 PM User is offline

Is there a way to test expansion valve? I am wondering if that might be a problem? It been a two year problem and it is starting to get wrost this spring for what ever rason.

The problem happens when the compressor is not engaged. I turned the fan speed to ¾ high and the compressor disengages. The high side starts going down from 130-to about 115-120. I stop filling cool air when the low side hits 35, but the compressor does not in engage for about another 15 seconds when it hits 45 on the low side which seem to take a long time. When the compressor engages it pulls the low side down to 20 psi for a sec then it slowly goes up to about 25-27. Also I put my ear to the lines when the on the low side and it sounds like it is flowing though the pipe after the compressor disengages, but when it gets close to 35 “5 secs” the flow sounds really slow. I don’t know if there is a dryer on this system but I think something is slowing the flow. The pressure on the high side is low because it was 70 with 25 % humidity. The high side port is after the evaporator so I don’t think it is the evaporator. If I bring the rpms up to 2200 which is drive speed the problem happens when the fan is on high as well.

This was the same problem I had before pulling a vacuum with higher pressure but it was 80 that day.

mk378 on Sun April 25, 2010 1:23 PM User is offline

If the compressor stops, it's not the expansion valve. Obviously, with the compressor stopped you're not going to get cold air. This would appear to be an electrical problem or possibly the clutch gap (though that usually is worse in hot weather).

It normally takes a long time for pressures to equalize on a TXV system. As soon as the compressor stops the valve should fully close.

seamonkeys1 on Sun April 25, 2010 6:15 PM User is offline

The compressor engages fine but turns off and on under low cooling needs normal about 30 secs on and 30 secs off. Example cool outside or lower fan setting or engine at driving speeds and under 80F. I was thinking this was normal for the compressor to do this under low cool needs or am I wrong? Where should I be looking?
The said problem happens only when the compressor is off. Seems like it need to turn back on when low side get close to 35 psi but doesn’t turn on until about 45 psi. What does tell the compressor to turn off and on under low cooling needs?

mk378 on Sun April 25, 2010 8:16 PM User is offline

TXV systems that cycle are controlled by temperature not pressure. There should be a temperature sensor on the evaporator. Being a 2005 model, there's bound to be at least one computer involved.

First though I'd check if the clutch is getting power when it is not engaged but it should be. If so it might just be the clutch gap.

Edited: Sun April 25, 2010 at 8:20 PM by mk378

seamonkeys1 on Sun April 25, 2010 9:30 PM User is offline

Turn on right away when power is provided.
Went ahead and bypassed the relay and stayed on the whole time problem went away stayed cold the whole time. It is looking like it is the Temperature sensor. Is there away to test this?

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