air conditioning

[babycritter]

my 1996 grand am the air conditionercompressor come on in max,a/c,defrost&heat. Is that a relay or the control unit?

 

[melsg5]

It's supposed to come on for all those settings accept heat. Are you sure you dont have the A/C button pressed to the ON position.

 

[babycritter]

thanks

I have no a/c button.

 

[melsg5]

Yes you do, guess you dont have an owners manual. Here is a copy for 99, look at page 3-3

http://www.vadengmpp.com/owners-manual/pontiac/1999-Pontiac-GrandAm.pdf

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[babycritter]

button

My's a 1996 grand am. I have a button in the lefthand for rear-defrost. But thanks.

 

[melsg5]

What position is the right hand dial on when the center dial is set for heat and the compressor is running?

 

[babycritter]

air

The heater, heater&defroster,defroster.

 

[melsg5]

In the defrost position the compressor is supposed to run. When the center dial is in the heat position and the right side dial is pointing to the floor have you looked at the compressor and observed the clutch engaging and are you getting cold air only from the floor vents? Is the link below an image of your controls?

http://carphotos.cardomain.com/ride_images/3/294/1721/25733360002_large.jpg

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[melsg5]

I did a test this weekend on my car. It is a 2008 G5, the Grand Am system may work the same way. When I place the selector dial exactly on the position for air directed to your feet, the compressor engages. If you shift the dial one click towards bi-level the compressor disenages. Thus you would get the compressor to run in feet only, defrost and defog regardless if the temperature gauge is pointing to hot or cold.

 

[BeStPRoGiE]

Not sure exactly if your talking about it not working on lower settings (0, 1, 2)
but then it only works on high. (3)

If this is the case then you want to check the fan motor blower resister which is usually located under the passenger side glove box. Mine wouldn't work on 0, 1 or 2, and only worked on 3 until i changed it.

Hope this helps.

 

[babycritter]

Thanks, I guess it works the way it's suppose too. It just doesn't seem right. I never thought that the compreesor comes on in defrost.

 

[Kevlar]

One of the attributes of air conditioning is dehumidification, that's why the compressor engages when defrost and defrost/floor are selected.

As heat is extracted from the cabin air, the moisture is extracted too. This is the condesation we see pooling beneath our cars, usually behind the right front wheel. I usually do a double take and make sure it isn't antifreeze!

The dehumidification is the reason defrost is so effective.

Hope this little diatribe helps.

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[babycritter]

Yea that helps.