Insufficient a/c question
Thread Starter
Cruising
Joined: Aug 2019
Posts: 10
Likes: 0
Insufficient a/c question
New to me previously neglected 2000 corvette came with many problems. Been sorting through them. Finally got the a/c to work after scratching my head and using forum searches. I ask this question because I have no point of reference. The compressor runs, the air coming out of all vents is nice and cold. Checked the refrigerant charge and it is at 45 psi on the low side and 350 on the high side. Seems within normal to me based on past experience and as I said, the air is cold. Also, all fan speeds work with noticeable increase in speed for each setting. Air blows out of all locations with change of dial (btw manual system). But, the car never really cools. Now to be fair, it is Florida and 97 degrees and the car is black on black but, my crappy hyundai gets much cooler. The only thing that seems off to me is that the amount of air blowing out of the vents seems low even at the highest settings. Are these systems marginal or do I have a problem? Opinions appreciated. Thanks, PaulO
Drifting
Joined: May 2008
Posts: 1,693
Likes: 490
From: Denver, NC
If the pressures are that at 2000 RPM, I think they are a bit high. Overcharged can cause poor cooling. There are some great AC guys here, I used this post when I checked mine and it's been really solid.
Humidity plays a pretty significant part in it too along with temp and pressures.
https://www.corvetteforum.com/forums...-ac-101-a.html
Humidity plays a pretty significant part in it too along with temp and pressures.
https://www.corvetteforum.com/forums...-ac-101-a.html
Last edited by Ed Ramberger; Sep 6, 2019 at 09:34 PM.
Safety Car
Joined: Mar 2017
Posts: 3,765
Likes: 938
From: Orlando Florida
Your vacuum valves are switching correctly, i.e. you can set for dash vents without massive air flow also coming out of the defroster or floor vents? If the vacuum valves work, then I suspect you're finding out what having the exhaust directly under the center console and torque tube does for HVAC effectivity...
Don't try keeping a Hershey bar in the console.
On the other hand, if the air is coming out of literally all the vents, then you have more Google searching to do, relative to a broken vacuum line under the battery tray.
Don't try keeping a Hershey bar in the console.
On the other hand, if the air is coming out of literally all the vents, then you have more Google searching to do, relative to a broken vacuum line under the battery tray.
Thread Starter
Cruising
Joined: Aug 2019
Posts: 10
Likes: 0
Redzg - thanks for your reply. The air flow changes with the control and does not seem to come out anywhere it is not supposed to. Wondering if maybe the fan controller or a bad fan can produce slow fan speeds even though there is a noticeable difference when the fan controller switch is moved up or down the settings.
Drifting
Joined: Mar 2018
Posts: 1,365
Likes: 414
From: New Jersey
Both of those pressures are too high. My C5 was just checked by Rob. If I remember correctly my pressure was 30-35 lbs on the the low side and around 230 on the high side. A rule of thumb is that the high side should be twice the ambient temperature +50.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,497
Likes: 3,999
From: Cape Coral, Florida
Looks like an overcharge to me !!!!...with 96-105 on the temp and relative humidity greater than 40% you're looking at 31-35 on the low side and 221-305 on the high !!
Last edited by C5 Diag; Sep 7, 2019 at 09:02 AM.
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Melting Slicks
Joined: Jan 2009
Posts: 3,275
Likes: 739
From: Miami FL
If the pressures are that at 2000 RPM... ...I used this post when I checked mine and it's been really solid.
Humidity plays a pretty significant part in it too along with temp and pressures.
https://www.corvetteforum.com/forums...-ac-101-a.html
Humidity plays a pretty significant part in it too along with temp and pressures.
https://www.corvetteforum.com/forums...-ac-101-a.html
That post has proven very useful time and time again, especially the pressures chart it has, as well as the proper procedures for the readings to be meaningful 
According to the attached chart, for a 100°F temperature @ 2000 RPM, these are the expected pressures for the following values of relative humidity:
- 50%
- Low - 40
- High - 350
- Center Vent Temp - 69°F
- 60%
- Low - 43
- High - 360
- Center Vent Temp - 73°F
- 70%
- Low - 44
- High - 365
- Center Vent Temp - 75°F
It seems you're in the ballpark, considering the high humidity levels in Florida, but only if you took your readings at 2000 RPM.
I suggest you retake your readings following the procedure summarized below and report back
Although not essential, a Thermometer will give you a better idea of the A/C system health. You can get for around 5 bucks:
As mentioned above, take a look at this Post. It has detailed instructions to check/add refrigerant.
-These are the CliffsNotes:
First you'll need to find the current ambient temperature and humidity. Then, using the chart below, determine your target values for:
- High Pressure
- Low Pressure and
- Center Vent Temp.
Now proceed to take your readings. Make sure you take them with (otherwise readings will be affected):
- Engine @ 2000 rpm
- A/C in coldest setting
- Fan at maximum speed
- Both windows down
- Thermometer in center air vent
