So I've been getting to know my 1999 Vette over the past year and1000 miles of driving. Over that time I've always felt like the AC was "suggestive" of cooling the car, but not as convincing about it as my modern daily drivers. It will blow cold but in order to feel like it's doing much good I need to set the temp very low (67) and set the fan on MAX. It will after a couple of minutes blow cold-ish air. I've been dealing with since I frankly rarely need much AC here in Oregon. It's not that hot and I have the targa top off 75% of the time. BUT there are days where some AC comes in handy, like returning from a long show day in the sun.

This whole time I was thinking the system had a leak since I saw it was recharged a few years ago from the paperwork I got with the car.

This week I picked up a re-charge kit figuring I could fill it up and buy myself until next summer to get the system overhauled at a shop. I setup as explained, car running, AC max, compressor running. I plugged the included gauge in and it was reading "normal" say 37 psi. I squeezed the trigger just to see if that changed anything, probably got another oz in the system and it was reading closer to 40 psi. I took the gauge off and on a couple of times and it read the same.

SO, the system IS charged. Everything else in the HVAC appears to be working, heat blows in the winter, the vents all work and pushing the mode button changes where the air blows out. Not sure where to go next. It's not a high priority right now since I can get it work enough, but I'd be curious what I can try next. There's no codes in the DIC. I've read about blend-door actuators (did one on a 2001 Silverado way back in the day, when my old truck was stuck blowing hot only).

Anyone have a good comparison on how cold the air blows from their C5 vs their modern cars? I don't have a good reference point for that.

Could it be the blend-door just not completely failing? Other suggestions?

Thanks all!

 

I can give you a reference point on a 2003 C5 I just bought. I don’t have any newer cars, I just put a compressor and dryer on my 2004 GMC Sierra, vacuumed and recharged the system, the recirculation door doesn’t work so at idle on a humid 88 degree day here in Ohio I got about 44 degrees. My C5 is all stock and the recirculation does work on that, on the same day and at idle, hood closed, on the lowest fan setting I got about 34 degrees. My temp gauge is cracked in the picture but it’s a hair under 34 degrees.

 

Maybe lower the temperature setting. Mid 70s is a high hot setting in my opinion, mine during the summer is never over 70. Plus who knows how accurate a temperature reading actually is on those. Those systems start adjusting the air flow from pure cold to a mixture, fan speed, turn off recirculate long before they reach the setting temperature. So it's going to start putting less pure cold air out long before your setting. I'd crank it down to 68 or so and ensure the recirculate stays engaged and see how that feels.

 

I don’t have one handy at the moment, but there are a number of charts that show exactly what center vent temperature you should be getting for the current environment you (well, the car) are experiencing. The charts do show specific conditions, such as windows down, max A/C (i.e. 60), 2000 RPM, etc.

 

And the temperature as low it can go correct?

 

First thing I see is you have the temperature set to 76 so I assume you have the automatic climate control.

It will blow cold but in order to feel like it's doing much good I need to set the temp very low (76) and set the fan on MAX.

If your interior temperature setting is at 76, that is what your system will attempt to control your interior temperature to by adding heat to the cooled air. First thing to do if you want to measure your a/c outlet air temperature is to set your interior temperature as low as it goes which is 60 degrees.

 

This is a re-creation of an R134 pressure chart used several times on the forum -- I just redid it to be a bit more legible. 2000 RPM, windows down, temp. set to 60 or full cold, air inlet set to fresh, not recirculate.

 

Just checked mine 2 weeks ago with a fluke Pyrometer. 48 degrees at the center vent with 93 outside temp

 

I just had my system fixed after a compressor seizure at highway speed, pretty much everything but the evaporator was replaced. I checked the center vent temp a couple days after the fix and got 41 degrees. This was in 95 degree ambient with 60% humidity, gotta love Florida in August...

 

This is the FSM Performance Chart for an 01.

 

Thanks for the charts and the comparison values folks. I'm getting a vent thermometer in the next couple of days and will start checking what's coming out of each vent.

NOTE: Fixed my type-o from setting to 76 to 67. I agree 76 wouldn't do much to cool the car outside of exceptionally hot days.

 

Ok after further investigation I appears that my hot/cold work fine but the MODE switch isn't doing anything. The pictures on the display change but it seems like I have a medium amount of air coming form all the vents no matter what, nothing changes.

I see quite a few posts about the vacuum line issues, leaks that can cause this air driven actuator to stop working. My car is a 1999 and it def had a battery acid leak back in the day. Sounds like that's the next level of troubleshooting, tinkering for me! Ugh. Thankfully there's a number posts out there with some hacks to get those lines replaced.

 

Mine is doing the same thing. No matter the mode setting, air blows out all of the vents including defrost at the same time. Have you checked the dic for any HVAC codes? I used a scanner AND the dic and found no trouble codes so I'm going to have my shop do a smoke test for a vacuum leak.

 

This is probably the second most common issue to C5s, just after rocking seats. Almost universally a broken hard plastic vacuum line buried inside the wiring harness running from the passenger wheel well to the back of the intake manifold.
https://www.corvetteforum.com/forums...with-pics.html

 

No codes here either. I'm curious how it goes at the shop, I'm not above tearing the car apart to solve this, but I'm also not above paying someone a reasonable amount to tackle it.

 

I agree that paying someone else can sometimes be the best option. The key is finding a viable someone else. A corvette specialist may be more per hour, but may take fewer hours. Too many professionals consider looking up information on the internet unthinkable.

 

UPDATE:

I finally got the notion to have this looked at. I found a local shop that was willing to dive in. I gave them some tips on where to start. I guess they have a guy who is pretty good with GM cars. They were able to get in, pull the battery and tray (tray was shot from the old acid) get the line replaced and button it all up $600. A little over 3 hours of labor $150/hr and some parts. That seems NOT BAD AT ALL. Happy to have working vents for the summer season.