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Aircon turns on when switch to defrost

1897 Views 5 Replies 5 Participants Last post by  Merc6
Hello,

when I switch the ventilation to 'defrost' the aircon swtches on automaticly.
Is there a way to use the defrost setting without aircon?
I don't want to use the aircon all the time, without the aircon, it defogs enough.


Thanks!

Mark
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AC won't turn on below or around freezing outside temperatures.

Otherwise, no. It's a default on most models of cars to dehumidify the air blown at the windshield.
 

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Feel its totally worthless, even with the V5 compressor that does not cycle, and switching on the compressor in above freezing conditions with stiff PAG oil and brittle seals does nothing but wear out the compressor. PAG is water based. The ability for the air to hold moisture drastically decreases with ambient temperature.

And system pressures are very low, near the cutoff point so don't provide that much condensation at the evaporator to start with. So definitely a waste to switch on the compressor in defrost mode.

Depending on the system, would be just a tab on the mode switch in defrost mode where the 12V supply to the compressor wire could be clipped off, would work fine in the AC modes. No such switch on the Cruze, firmware in the BCM controls when the compressor comes one.

Being frugal and wanting my compressor to last, just crack open the drivers' window that keeps the windows clean until the vehicle warms up. Worse culprit for this is your own breathe plus the exhaled air from your passengers. Ha, could hold their breathe.

Is should not switch on if the ambient temperature is below 40*F, but engine heat changes this number. From good advice from American engineers in helping the Japanese design a good reliable AC system, when the AC switch is off, it stays off.

Guy could add resistance to the high side thermistor to fool the computer into thinking it too cold for AC, but some experimentation would be necessary. Then bypass that resistor when AC is needed.
 

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The ability for the air to hold moisture drastically decreases with ambient temperature. And system pressures are very low, near the cutoff point so don't provide that much condensation at the evaporator to start with. So definitely a waste to switch on the compressor in defrost mode.
I live in a valley so say my car is parked at 35F degrees all night, I drive three blocks up hill its 40F outside & all my windows instantly fog with a cold car. That AC being on is the only thing that actually can handle this situation.


Being frugal and wanting my compressor to last, just crack open the drivers' window that keeps the windows clean until the vehicle warms up. Worse culprit for this is your own breathe plus the exhaled air from your passengers. Ha, could hold their breathe.
This is why I love my weathertech vent visors, even on a rainy day I can just crack a window. Driving through hills and valleys especially with a high dew point though even with all 4 windows cracked, only the AC will defog the wind shield. Having the heat on helps, but I don't need heat when its above 40F outside.

Real simple solution is to make the system work like my 2004 cavalier did, any time the AC is on the AC button is lit. If you want to turn it off your more than free to do so. It still turned on automatically with defrost, but at least it told you it was on unlike the cruze.
 

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40*F is the point of compressor lock out and outside air is used to defrost and dehumidify the inside cabin of the car. Once you get hot enough to not fog the windows, try to switch from it as it eats gas when it is above 40*F. This may make your in city MPG tank some for no apparent reason o top of winter gas mix.
 
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