Climate Control becomes ineffective after an hour ..
Thread Starter
Advanced
Joined: Sep 2010
Posts: 86
Likes: 4
From: Hampstead NC
Climate Control becomes ineffective after an hour ..
Having rebuilt a 1994 Corvette with my son over the last year (more general info can be found here on that topic), we started the long journey home from Oceanside, CA to Midland, MI via Holden Beach, NC two weeks ago.
When we got into the desert region outside of San Diego, it was time to use the rebuilt and recharged AC ... the car has climate control, so set it to 60degF and pressed auto, and it worked fine. An hour later, nothing coming from the vents, but you can feel cold air leaking from the passenger foot well, and heater fan can be heard running full speed. Pressed every button on the control panel ... vents, footwell, screen ... all to no avail. So we turned off the climate control and opened the window but with the outside temp at 102degF, not much help.
About an hour later, when stopped for gas, and baking hot in the car, I tried the AC once more ... worked fine!
We soon learned that you could use the climate control for about an hour and then it got confused and didn't issue any air from any vent. Let it rest for about 15-20 minutes, and bingo, working once more!
Any thoughts on what might be causing the loss of function after a period of time?
Thanks, ATG
When we got into the desert region outside of San Diego, it was time to use the rebuilt and recharged AC ... the car has climate control, so set it to 60degF and pressed auto, and it worked fine. An hour later, nothing coming from the vents, but you can feel cold air leaking from the passenger foot well, and heater fan can be heard running full speed. Pressed every button on the control panel ... vents, footwell, screen ... all to no avail. So we turned off the climate control and opened the window but with the outside temp at 102degF, not much help.
About an hour later, when stopped for gas, and baking hot in the car, I tried the AC once more ... worked fine!
We soon learned that you could use the climate control for about an hour and then it got confused and didn't issue any air from any vent. Let it rest for about 15-20 minutes, and bingo, working once more!
Any thoughts on what might be causing the loss of function after a period of time?
Thanks, ATG
Burning Brakes
Joined: Sep 2010
Posts: 935
Likes: 385
Sounds like your evaporator is freezing up. Make sure the evaporator drain is open and water is draining on the ground when the air conditioner is operating.
When the water that condenses on the face of the evaporator can't drain from the enclosure, it can have a tendency to freeze in the evaporator fins, especially if you have the temp turned to way down.
When the water that condenses on the face of the evaporator can't drain from the enclosure, it can have a tendency to freeze in the evaporator fins, especially if you have the temp turned to way down.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Sounds like you could be losing vacuum to the vent system. Look at the vacuum check valve under the right side plastic cover of the engine. You will see a black valve with 3 hoses to it. Check to see if it is broken or cracked. If it is bad, then that is your problem.
It is a $5 part and a common item that goes bad. This valve can also affect the cruise control.
It is a $5 part and a common item that goes bad. This valve can also affect the cruise control.
Thread Starter
Advanced
Joined: Sep 2010
Posts: 86
Likes: 4
From: Hampstead NC
Sounds like your evaporator is freezing up. Make sure the evaporator drain is open and water is draining on the ground when the air conditioner is operating.
When the water that condenses on the face of the evaporator can't drain from the enclosure, it can have a tendency to freeze in the evaporator fins, especially if you have the temp turned to way down.
When the water that condenses on the face of the evaporator can't drain from the enclosure, it can have a tendency to freeze in the evaporator fins, especially if you have the temp turned to way down.
The weirdest part of the problem is the fact that I cannot get any airflow (cold or hot) from any vent when I press the various buttons on the climate control panel ... it is as if air flow is just not getting through to the distribution system! You can hear the fan running flat out (it shows #10 on the panel), but nothing comes out of any vents. Would a blocked evaporator block air flow through to the distribution system?
Last edited by atgordon; Oct 11, 2011 at 10:36 AM.
Thread Starter
Advanced
Joined: Sep 2010
Posts: 86
Likes: 4
From: Hampstead NC
Sounds like you could be losing vacuum to the vent system. Look at the vacuum check valve under the right side plastic cover of the engine. You will see a black valve with 3 hoses to it. Check to see if it is broken or cracked. If it is bad, then that is your problem.
It is a $5 part and a common item that goes bad. This valve can also affect the cruise control.
It is a $5 part and a common item that goes bad. This valve can also affect the cruise control.
Before we left SoCal, I did change one of the vacuum lines to the check valve (the one that runs to the side of the block), and I did have to cut back the larger hose and splice in a new piece (about 3" long) since it was weathered and split where it joined the check valve.
I'll think I'll go ahead and change the check valve just in case ...
Last edited by atgordon; Oct 11, 2011 at 10:44 AM.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
I did look at this part, and it looks OK. Cruise control works perfectly for hours and never varied in performance for the whole trip.
Before we left SoCal, I did change one of the vacuum lines to the check valve (the one that runs to the side of the block), and I did have to cut back the larger hose and splice in a new piece (about 3" long) since it was weathered and split where it joined the check valve.
I'll think I'll go ahead and change the check valve just in case ...
Before we left SoCal, I did change one of the vacuum lines to the check valve (the one that runs to the side of the block), and I did have to cut back the larger hose and splice in a new piece (about 3" long) since it was weathered and split where it joined the check valve.
I'll think I'll go ahead and change the check valve just in case ...
I bet you've got more splits in the vacuum line....best to check the entire hose.
Thread Starter
Advanced
Joined: Sep 2010
Posts: 86
Likes: 4
From: Hampstead NC
Did a check today, and I do have a puddle under the car when running the AC.
Is there any way to check if the AC bleed line is partially blocked? How do you clear the fluid drain from the evaporator?
Is there any way to check if the AC bleed line is partially blocked? How do you clear the fluid drain from the evaporator?
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Racer
Joined: Jul 2002
Posts: 285
Likes: 1
From: Edmond Oklahoma
Also, many GM products use a "filter" over the evap core that can attract/trap debris and dirt, restricting airflow through it. If this is the car that sat under a tarp (think it is), vermin may also have nested there.
Last edited by a454corvette; Oct 12, 2011 at 12:54 AM.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
I would also check the A/C compressor and see if it is cycling. Raise the RPM a bit and see if the clutch releases. If it does not, the cycling switch may be bad.
If the cycling switch is bad that causes the coil to freeze up, it usually happens during high speed driving because the engine is running at a constant higher RPM. It may not show up around town.
