Weird AC issue

When its cool outside <85 degrees my AC will blow ice cold, but when it gets hotter outside it won't blow as cold and it seems that the evaporator tends to freeze up. I think I need a new expansion valve but the problem seems conflicting. Also sight glass is nice and clear. Anyone got an idea?

Thanks

 

That's odd.....usually evaporator freeze up is caused by either being too low on refrigerant or perhaps your POA valve has too low a setting. One more thing that could be happening is you have moisture in the system, which freezes at the orfice in the expansion valve and blocks it off just enough to make the evaporator get below 32* and it then freezes over. Evap pressure is directly related to output temperature. Since the compressor is sucking, if the refrigerant can't get through it makes a vacuum.

Here's how I'd go about checking this. Check your low side pressure. Do this with the engine running at 12 or 1500 RPM and a huge fan directed at the radiator. You may need to run it like this for over 20 minutes, and you need to keep the condenser cool.

Typically anything below 28 PSI will cause freeze up. (unless you are using 134, not sure but I think if the POA was re-calibrated that would be 26 psi). If I had to guess, I'll bet that test will show very low pressure, and can even go into a vacuum. That would indicate to me that there is definitely moisture in your system, freezing up the exp valve, and you will need to discharge it, replace the drier (very important) and then evacuate it really well. Then re-charge with refrigerant. :TU:

Here's another reason why I like Duracool so much......if it gets wet, it won't form acid and eat out the guts of your system like R-12 or 134 will.

Oh.....I forgot.....be sure to discharge responsibly. (seriously)

 

Thanks for the information. Too bad I don't have any gauges or method of discharging responsibly without costing :dollar:

 

Anybody who can use tools and has mechanical aptitude can do a/c work. You will need a cheap set of guages and an evacuator pump. They make air powered ones or you can make one from an old refrigerator compressor. Yes, you should discharge the old stuff responsibly, whether you agree with the reasons or not. I would be inclined to think that your local a/c shop would be willing to do that for you if you feel strongly enough about it. I don't think the EPA hovers around in helicopters with air snifers looking for DIY mechanics who might dump a little noxious gas into the air on a one time restoration. These people can't even catch the terrorists. But for the sake of Al Gore's global warming it's best to keep a clear conscience. p

The Gods here should make a sticky reminding everyone to dispose of old refrigerants responsibly.

Maybe over the winter I'll write a DIY thread about how to get an old system up and running from scratch. For what you'd pay a professional you can buy your own stuff and over time it will pay for itself. If you can do your own tune ups you can do an a/c recharge. Professionals like to intimidate DIY car guys into thinking this is rocket science punishable by life in prison. You'd be surprised how easy this is to learn once you understand the basics.