# Need help. I need a/c vent temperatures.



## justin-branam (Oct 31, 2008)

So my a/c suddenly has gone whacko but the dealership claims there is nothing they can find wrong with it. It blows ice cold on recirculator, but it blows warm and the refrigerant never even gets cool when the a/c is set on fresh air. 

The temp here in Houston has been running in the high 90's in the day. I am trying to get temps coming out of the a/c vents (stick the thermometer right up next to or in the vent) after the car has been running for 20 minutes or so and is warmed up to running temps for a few minutes, with the a/c set to fresh air (dash vents and floor is what ive been testing) on blower speed 4. Also it would be helpful to know on this setting, what your ac lines running into the firewall are like. my low pressure (larger diamter) line is warm and bone dry (not sweating at all), and my high pressure line (small diameter one) is so hot you can't touch it without burning yourself. of course if i run the a/c on recirculator, the low side is cold and dripping sweat and the high side is barely warm.

The dealership said they had another GTO and it did the same thing so it must be normal, but since mine hasn't done this until just a few days ago, i find it hard to believe its "normal". i want some hard data to take and show them. any help you guys can give me would be greatly appretiated. below is a quick form you can copy and paste to fill in any info. thanks again for ny help or data you can give me.




Model year of GTO:

Outside air temperature:

Time car has been running with a/c on (using setting requested):

Temperature of air at a/c vents:

Low pressure pipe at firewall (hot or cool, wet or dry):

High pressure pipe at firewall (warm or boiling hot):





Thanks again everyone!


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## fergyflyer (Apr 18, 2005)

They make thermometers that you can stick in the vent. Buy one of those. 

With the car idling in the shade and the fan speed set to the 2nd spot and the controls put on fresh air you should get a 20-25 degree temperature drop from the outside temperature. Most dealers will tell you that 15 degrees is acceptable, but it really isn't in my book. 

Here are some variables. If you have the fan speed higher than the 2nd spot you have too much airflow for the system to properly cool. If you have the fan speed set lower the airflow will be slower and there will be a greater temperature drop. If you set it on recirculate then you are cooling inside air which is cooler than the outside air and will eventually get a real cool temperature but won't tell you if the system is working properly. 

Check your temperature drop and if it isn't acceptable then make them recharge the system or find out what performance issues your system is having. 

Also, living in a hotter climate it's not a bad idea to have the system evacuated every 4-5 years and fresh R-134 and fresh lubricant put into the system. The R-134 doesn't wear out, but debris from metal parts wearing get into the system and evacuating it will help to clear it. The lubricant does wear out and changing it will save you big bucks down the road.


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## justin-branam (Oct 31, 2008)

fergyflyer said:


> They make thermometers that you can stick in the vent. Buy one of those.
> 
> With the car idling in the shade and the fan speed set to the 2nd spot and the controls put on fresh air you should get a 20-25 degree temperature drop from the outside temperature. Most dealers will tell you that 15 degrees is acceptable, but it really isn't in my book.
> 
> ...


thanks for the info. my buddy around the corner does home a/c repair and does lots of automotive work on the side. he checked everything he could. the system is actually a bit overcharged. i do have an a/c vent thermometer so decided to check the temps myself. here are my temp specs from today.


4:30pm
ambient temp: 99.2 degrees F
air out of vents: 67.5 degrees F
difference: 31.7 degrees F

10:30pm
ambient temp: 82.4 degrees F
air out of vents: 65.4 degrees F
difference: 17 degrees F

kind of wierd that the vent air only shows a 2.1 degree difference while the outside temp shows a 16.8 degree difference.


im pretty sure i know what is causing this, i just dont know why it is happening. The refrigerant is not being cooled properly and is not able to expand enough to produce cold air. like i mentioned, the low pressure side is barely below air temp and the high side is so hot it will burn you and leave a blister. on pretty much any car, you should be able to hold onto the high side and it may be a bit warm, but shouldnt even leave a red mark. all the system is doing is circulating hot refrigerant. however if i let the car cool, and run on recirculate, the coolant is ice cold. low pressure side hose is cold and has tons of condensation, and the high side is barely warm. the second i turn it over to fresh air, everything heats up like crazy. it really seems to me that somewhere there is a bad relay or something. this just is not right. AAAHHHHHH!


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## fergyflyer (Apr 18, 2005)

The symptoms you describe would indicate that the airflow over the condensor is blocked. But that would affect the recirc as well. 

Check your cooling fans to make sure they are coming on properly on recirc and fresh. 

Those temperature reading, are they from fresh or recirc????

I've had issues with the fresh side freezing up on high humidity days on several cars. I'm not sure what happens, but the symptoms are the airflow decreases and the air is less cool. I'll turn the a/c off and use just vent for a couple minutes till the airflow picks back up to normal and the problem goes away for a while.


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