AC performance humidity dependent, need help

[ruoknow]

The AC on my 96 Avy has been acting up on me for at least a year. the sympton is humidity dependent. When the sky is clear, with no clouds, the ac is really cold. It starts with cold air, last about 45 mins, then blows air with increased temperature. When there is a little clouds in the sky, the AC will start with cold, last about 20mins, then blows air with temperature graudally increase until reaches outside temperature. If it is very cloudy, then maybe 5 mins.....
This is not the situation with the slippery of belts. AC lights are not flashing when blowing warm. The magnet switch is still engaged when blowing warm.
Anybody knows an answer?
I am living in texas, almost can't live without a cold ac.
Thanks guys.

[project92camry]

have sumone check ur refrigerant by hooking up gauges to the system and see if it has proper readings on the high or low side. your gonna have to find the specs for your car to see if they fall within specs.

[Cyorke]

look sfor the sight glass at the front of the car. It is on the reciever/dryer that is normally mounted on the right hand side of the car as you are looking at i. It will be behind the grill. Cylinder shape with a/c lines going in and out. The sight glass is on the top. WIth the a/c on and the compressor running look for bubbles in teh sight glass. IF there are bubbles then the refigerant is low. You can buy it at wal-mart, autozone or anywhere else for fairly cheap if you need some. follow the directions on teh can and you will be good to go. When filling it as soon as you see no bubbles you need to stop the flow of the refigerant into the system so as not to overcharge it. THat can be as bad as the system being undercharged.


IF you check and there are no bubbles then you need to take it somewhere to be tested by someone that knows tha they are doing. Like ^^^ said they will need gauges and others tools that most people do not ahve a need for.

[ruoknow]

Thanks guys.
Today, it lasted for 25mins without a problem. My concern is that the shop guy will not find anything wrong since it is not repeatalbe sometimes. I guess I am going to buy a gauge and test it by myself.
I suspect the problem is the dryer. Because when it is saturated with water, the expansion valve is gonna be frozen up. No freon circulation anymore.
if i decided to fix it, i will buy a vaccum pump from ebay. Upon fixing it, i will sell it. So it is like rent a tool. of course, i will buy a pair of gauge using the same method.
what do you guys think?

[ruoknow]

Yesterday, it's cloudy. My AC quitted working eventually, so I got a chance to check it up. I let my wife sit in the car and turn the AC switch on and off. All the time during this checkup, the AC was blowing warm air. I was standing over the engine bay......
1. When wife turn the ac on, both the fan and compressor kicked in. When she turned it off, both stopped. Conclusion: electrically, the AC operates normally.
2. When the compressor was working, the sight glass showed a little small bubbles from time to time. But most of the time, there was no bubble. It's clear inside the sight glass. According to the ice cold performance when it works, I doubt there is low level of R134a.
3. My guess is somewhere clogged in the AC system. In the AC components, the most possible candidates are dryer/receiver and expansion valve, since they are the only two to control the r134a flow. The prices for both are around 30 bucks at oreily.
4. This symptom (sometimes cold sometimes not) has lasted over a year without serious development. I doubt there is a leak in the system, but i am not sure. My question is: since the AC circulation is supposed to be an isolated system, it should not be weather related. I mean if the dryer is oversaturated, the AC should not work properly all the time. Or the expansion valve is corroded up, the AC shouldn't work all the time. It just can not be humidity dependent, right?
If i go ahead to change these two parts, how much chances I will make this work? Of course, I will collect all the tools, such as vacuum pump and gauges, neccesary for the project.

[jhbhatia]

I think you just need to fill your refirgrant! if it was those parts, then your a/c shouldn't be blowing cold at all right? Where in TX you at? if anywhere near houston..and if you buy a 11-20 can from walmart/target..I have the a/c refirgrant filling tap lines you can borrow!

[ruoknow]

jhbhatia, it's so nice of you. I live in dallas. Thanks so much!
Your reply sounds reasonable too. I am just wondering that I can see the refrigrant flowing through the dryer, but the air blowing out was just like no AC (even not cooller a little bit than room temperature). So, apparently the refrigrant is not passing the evaporator. Then something blocks the flow of refrigrant before it reaches the evaporator. The only two parts are dryer and expansion valve......
I don't know....... When it performs well, the air blown out is really ice-cold though.
Another reason is that I don't want to overcharge the system.

[Kep]

OK, I'm no expert so verify this. However, it is my understanding that if the evaporator (that's inside the car cabin, right?) gets too cold that it will ice up. This blocks the air flow and, consequently, won't cool the cabin. This happens much quicker on hummid days than dry days. I believe that this can happen if there is too little 134A or if the expansion valve is malfunctioning.

I also understand that 134A AC systems are much more sensitive to the appropriate amount of refrigerant. You're not supposed to just add in more gas. You're supposed to evacuate the system and then add in the proper amount of 134A by weight, not by pressure.

If you learn that you have the correct amount of 134A and it still doesn't work then suspect a malfunctioning expansion valve. I just can't see there being enough contamenants in the system to plug up the dryer enough to matter.

Usually when you park a car after the AC has been running it will drip for 4 or 5 minutes. If I am correct and it is icing up I would expect the car to drip a lot longer (until the ice melted). This might be a way to test it.

Hope this helps,
Kep

[jhbhatia]

Originally Posted by Kep

I also understand that 134A AC systems are much more sensitive to the appropriate amount of refrigerant. You're not supposed to just add in more gas. You're supposed to evacuate the system and then add in the proper amount of 134A by weight, not by pressure.

That is how the dealership do it, but thats not the way, i've done it in the past and this includes my personal exp with gen4 camrys'. Surely i'm NO TECHNICIAN, but my approach has seem to make a difference to my camry! And not to mention, it was cheap!

What you propose is not too off bat, its a better approach, but i guess i'm cheap. Let the dude try it with a $11 can before we have him spend 2 bills.