Car: 2000, Mileage 20,500, Owned Since April 2005. No History Of Hvac Problems That I Am Aware Of.

Problem:

When I Set The Thermostat To Max Cool And Push The 'auto' Button, Usually The System Will Come On Blowing Cold Air And Will Have The 'inside Circulation' Button And 'air' Button Illuminated. Sometimes It Is Just The 'inside Circulation' Button That Is Lit And The 'air' Button Blinks Or Goes Out. When I Push The 'air' Button Back On, It Will Blink For A Bit Then Go Out. The System Is Then Blowing Hot Air.

Yesterday, I Had The System On Auto And It Was Blowing Ice Cold Air. Then All Of The Sudden, The 'air' Button Was Off Or Blinking And The System Went To Blowing Hot Air.

As I Read The Owners Manual It Says The 'air' Light Will Blink If The System Is Low On Freon. How Can The System Be Blowing Ice Cold One Minute And Then In A Heartbeat, Convert To Hot Air If The Freon Is Low? It Seems To Me If It Is Blowing Cold Air At Least For A While, The Freon Would Be Okay.

I Normally Set All My Gm Air Conditioners To 70-72 And Run Them On Automatic.

I Tried Manual Operation With The Same Results. I Have Always Had Great Success With Gm Air Conditioning Systems Until I Experienced The Operation Of This One In The 'vette.

It Seems To Me If The Hvac System Had A Problem, I Would Get Some Sort Of Code Warning On The Dic. This Isn't Happening.

Anyone Else Experience Any Problem Such As This Or Can Anyone Tell Me What My Next Move Should Be?

 

Good luck

 

I am not positive but you may be low on freon.If your vehicle is almost six years old,I am thinking that for a start bring it to whomever you use as a mechanic and have the system tested.Is your vehicle under some sort of extended warrantee?If so,I am certain they will fix it for free or for a deductible.Your Hvac system may have a history of repair that you are unaware of.I am sure lots of other people here on the forum can help you with more information,but that is my guess.Goodluck

 

You should pull the codes to see if there is one for the HVAC system.

To do that is simple...
Here is one site http://www.corvetteactioncenter.com/...ad.php?t=72535

 

Any one else???

 

Did you pull the codes?

 

Systems that are low on Freon will usually produce very cold air (at least for a while), often below freezing. This is unfortunate, as this mayl eventually cause an evaporator to freeze up and prevent any air flow at all.

What may be happening, is that your system is low but it takes a short while for the LP sensor to figure things out and shut down the compressor.
Hence the switch from ice cold air to hot air.

Suggest you get some gauges and hook them up. As a starting point, you need to be seeing 30 to 40psi on the low side when the compressor is running. The low side is the cold one near the battery box.

Let us know.

Dave
P.S. did you pull the codes yet?

 

I agree with maskell. When the suction pressure gets too low, it causes the compressor to start cycling. When the cycling is excessive, the system permanently shuts of the compressor so there is no longer any air cooling at all. If you add a can of 134a and reset the system, it should be normal again. I am ot sure how to reset the system on a C5 (on a C4, it involves pulling some fuses). Good luck.

 

I appreciate all of the information I am getting. I haven't pulled any codes yet, but met up with some fellow C5'ers yesterday while traveling the weekend car show circuit. The concensus was low freon. I will possibly look for some codes this week, but in the end will probably schedule the car for an ac and freon check. I am hoping that is the problem. If not, I'm sure there is a code locked in to give me a hint as to the next move.

 

With reference to the codes: I ran a code check and had absolutely none, zero, nada. Not even in the history. I paid particular attention when the HVAC section came up. After all the sections flashed by, the summary said NO CODES. So I guess it will be a system check of the freon.

 

Here's one simple thing to check as well. What does the external temp read on the display when the AC blinks and shuts off? The external temp sensor plays a key role in allowing AC to operate.

This sensor commonly fails due to moisture/corrosion and reports an erroneous external temp. If it reports an external temp below 35F-40F it will prevent the AC from operating (see page 3-8 in your manual).

This is a very common problem. If this is your case and your display is showing erroneous values, simply unplug the sensor and the system will default to an external temp reading of about 58F which will allow AC to work. The sensor is located below the passenger headlight - you can see it protruding under the nose of the car in front of the radiator cavity on the passenger side. There's a connector right next to it that you should be able to reach with the hood up and the headlight raised. A replacement sensor is only about $12. Also, the connector may itself have corrosion and be part of the problem so check that as well.

If this is not your case, then freon is the next likely thing to check.

 

John,

It is interesting that you mention the outside air temp gauge because it does read (mostly) a constant low temperture. I guess I should look in the manual as I would have never made that connection. I have been meaning to look at the sensor to see if it was obstructed or dirty. I will look into it as well as put manifold gauges on the air freon system.

Thanks,

 

FYI........I disconnected the outside air temp sensor and the gauge defaulted to 62 degrees. The air conditioning is now working as it is supposed to. I will order a sensor today and have the system freon checked during the next garage visit.

Thanks for everyone's help.

 

Great!

Glad when things work out!

 

UPDATE: Installed the outside air temp sensor today and it is about as accurate as my Eldorado temp......pretty close. The air is now back to working fine. GM Part was $8.50. Thanks to all.