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The details are in the details feild

Tiny
ESSAMSHAWKY
  • MEMBER
  • 2005 CHEVROLET OPTRA
HiI have an Optra-Forenza-Lacetti, 2005, 1600cc
Lately I've made some repairs to the AC system that included replacement of the following:
Dryer, High pressure valve (plugged inside the compressor)
High pressure pipeline

Now what happens is:
At low fan speeds (1, 2) the systems freezes up. After 30 mnts of driving poor airflow + high temp in the cabin.
At high fan speeds (3, 4) everything is just find except that I suffer a very cold air hitting my face (colder than what I'm used to get b4)

What I do to solve this is turn the compressor off till the ice melts down then turn it back on

Thanks a lot for your help
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Monday, September 24th, 2012 AT 12:20 PM

13 Replies

Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
The thermosensor circuit is not working correctly and this resullts in the cooling coil icing up. Recheck the thermosensor location and installation. Try turning the temperature to a higher setting.
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Monday, September 24th, 2012 AT 12:37 PM
Tiny
ESSAMSHAWKY
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Thank you
Can you please explain what you mean by the thermosensor?
Do you mean the low pressure switch? Or just the temp controller switch?

One more thing, setting the temp to high doesn't prevent icing up on low fan speeds.
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Monday, September 24th, 2012 AT 1:26 PM
Tiny
KHLOW2008
  • MECHANIC
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Not the switch. It is the sensor tht has its base plugged in between the cooling coil fins. That is teh temperature control sensor, usually called the thermostat.

How high did you set the temperature? If setting does not help, you might need to replace the thermosensor or check if it is bad and not sensing correctly.
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Monday, September 24th, 2012 AT 1:49 PM
Tiny
ESSAMSHAWKY
  • MEMBER
  • 8 POSTS
Thank you very much, I referred to the service manual of the car which I normally use in such cases and found out that my AC system doesn't include such thermosensor
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Monday, September 24th, 2012 AT 3:31 PM
Tiny
KHLOW2008
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There must be a sensor to sense the temperature of the cooling air for temperature control.

In this vehicle I believe is called the inside air temperature sensor.
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Monday, September 24th, 2012 AT 4:00 PM
Tiny
ESSAMSHAWKY
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I will recheck and get back to you.
Thank you vey much
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Monday, September 24th, 2012 AT 5:32 PM
Tiny
ESSAMSHAWKY
  • MEMBER
  • 8 POSTS
It's not there sir, I am positive
the system depends on the low pressure transducer and tge high prissure switch attached to the compressor only. No thermistate at all
I can attach an image to prove that. But it seems that my AC system is not the one in ur mind

thank you
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Monday, September 24th, 2012 AT 5:46 PM
Tiny
KHLOW2008
  • MECHANIC
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Is your system manual or automatic HVAC?
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Monday, September 24th, 2012 AT 5:56 PM
Tiny
ESSAMSHAWKY
  • MEMBER
  • 8 POSTS
Manual
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Monday, September 24th, 2012 AT 6:08 PM
Tiny
KHLOW2008
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Ok, this system uses the heater for temperature controls and attached are the procedures for diagnostics.
Images (Click to make bigger)
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Monday, September 24th, 2012 AT 6:39 PM
Tiny
ESSAMSHAWKY
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First of all I would like to thank you very much for your time and effort spent on this.

Secondly, it seems that you didn't get the idea correctly.

- My AC is perfect, I can say it's even colder than usual
- When the blower fan is on 1 or 2, the system begins to create ICE on the low level line and on the internal condenser, which stops the airflow and causes rise of capin heat.
- When the blower fan is on 3 or for, the speed of the blowing air prevents the ICE from being created. That's why no ice on high speed fan.
- I twice replaced the high pressure switch (within the compressor). The first time wasn't original but the second time was a GM part.

Now, I hope everything is more clear

One again thank you very much for your time and effort
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Monday, September 24th, 2012 AT 6:52 PM
Tiny
KHLOW2008
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Icing/frosting of cooling occurs only when it is too cold and the procedures shows what to look for.
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Monday, September 24th, 2012 AT 7:59 PM
Tiny
ESSAMSHAWKY
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I will follow that
thank u very much
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Monday, September 24th, 2012 AT 8:00 PM

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