A/C question

The A/C in my 2003 Corolla got weaker today (the cold was not as cold as it normally is).. The weather in NJ was about 85 and very humid.
My question is: Can the A/C ice up the way a home A/C can? If so what is probable cause and fix? Answers from your experience or technically knowledgeable folks would be much appreciated.
TIA
LB
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On Sat, 16 Jul 2005 00:05:05 -0400, snipped-for-privacy@nospam.info wrote:

Yes, the evaporator core can ice up, especially on those really sticky muggy days when the coils are wringing buckets of water out of the air. The AC Amplifier module is supposed to monitor the evaporator coil temperature with a thermistor, and cycle the compressor to prevent ice-ups, but it might be adjusted a bit too low.
Or someone clueless could have crawled under the dash and adjusted the setting, thinking they found the alarm's glass break detector, and messed up the setting. Hey, it happens.
(I know better, then again I'm also the one that installed the glass break detector - and the best place for mounting it ended up being right next to the AC Amplifier module...)
A trained AC technician (dealer or independent) can find that little box up under the dash and easily reset the adjustment. I know where mine is, but I'm not sure exactly how to adjust it - and there are several slightly different variations by year and car model. I'd have to break out the book.
The instructions for setting the control are in the Factory Service Manual, but they're a $eriou$ inve$tment for one little adjustment. If you want to fiddle with it yourself, see if your dealer will make a copy of that page for you. Or just copy the important parts like which way is colder, and what the proper setting procedure is - you'll need a good dial probe thermometer to check the temperatures.
--<< Bruce >>--
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Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
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"Bruce L. Bergman" wrote:

Thanks.
LB
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when low on gas they are more likely to ice up.
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"mrcheerful ." wrote:

Thanks
LB
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"mrcheerful

That doesn't compute...why is that?...
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Gord Beaman wrote:

When the refrigerant charge is low the evaporator coil is starved for refrigerant. Thisresults in reduced pressure at the inlet piston or expansion valve, thus allowing the refrigerant to vaporize at a lower temperature - below 32 degrees. At this point the first part of the coil will freeze. Then, since ice is a fairly good insulator the refrigerant will now travel further through the coil before encountering an exposed surface. More ice forms and the process continues. Gradually most or all of the evaporator coil will be covered with ice. This of course blocks air flow through the coil.
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Thank you Travis, this sounds reasonable (But I'm no expert in the a/c field)...thanks for a sensible explanation too, rather than some sarcastic shot.
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Gord Beaman wrote:

And today, weather just as bad or worse, did a lot of running around - about 200 miles - the thing worked just fine. weird.
LB
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The evaporator icing that others have described is the likely cause of the differences in AC effectiveness.
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Ray O
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Ray O wrote:

I figured that but now am wondering why it did it that one day <sigh> I wonder if turning it off and on too quickly caused a hic-cup. Home A/Cs do that.
LB
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snipped-for-privacy@nospam.info wrote:

Residential systems and auto A/C systems don't operate the same way. Your home system's compressor can be overloaded by turning it off and on again within a few minutes (like when there is a brief power interruption). Most new systems (and / or thermostats) have a timer to prevent this from causing the compressor to overload.
Auto A/C compressors don't have an equivalent timer. They are designed to operate in the 'short cycling' environment commonly found in cars.
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wrote:

The occasional icing is more likely caused by differences in humidity, ambient air temperature, cabin air temperature, temperature setting on the AC, and fan setting.
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Ray O
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Ray O wrote:

In order for ice to form the evaporator temperature would have to be below 32 degrees F. If the system is charged correctly and the expansion valve is working properly, this should never occur.
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Sorry, upon re-reading my explanation, I guess it does sound like the factors I listed are the underlying cause of the icing, and that is not what I meant at all.
There is an underlying cause of the icing that could be caused by stuff that others have mentioned, like a faulty expansion valve or low refrigerant charge, or amplifier problem. That underlying problem is not a guarantee that the system will ice up every time it is used while the underlying problem still exists because of the factors I listed above.
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Ray O wrote:

Thanks for all the replies. If it happens again I will be back.
LB
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"mrcheerful" wrote:

Since when? Usually when there is a freeze up it is because not enough air is being cooled or the tempature of the air to begin with is cool enough to let the surface of evaporater freeze. When AC is on recirculate it is not too rare for a freeze up at low airflow settings too. In the old days, car A/Cs had thermostatically controlled expansion valves that limited freezups better, todays fixed ones offer a lot less protection against this.
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SnoMan wrote:

When did Toyota stop using TXVs?
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The A/C in my 95 Prizm suddenly got weaker also. When a refrigerant recharge was ineffective, my shop traced the problem to a bad expansion valve. They replaced it and now full cold is too cold and I have to set it a few notches back. :-)
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There is an open Special Service Campaign on 90-94? Yotas -- apparently something in the system caused the expansion valve to corrode and elak all the Freon. They will either add some anti-corrode stuff or if too late they will repolace the expansion valve , seals and Freon. Check it out at www.alldata.com. I had it doen on my 90 4Rnr and 93 Camry --- no charge for work even on 10+ year old vehicles! Its like SSC or SSP 001. You dealer can tell if it was ever done by entering the VIN.

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