A/C Controller Issue
Thread Starter
Intermediate
Joined: Aug 2023
Posts: 25
Likes: 28
From: Virginia
A/C Controller Issue
I recently replaced the compressor and finally have cold A/C. When starting the car, the controller directs airflow to all of the proper places. After I drive for a while, no air comes out of the vents. I can turn the car off and wait a while and then it starts directing the air properly again. I’m guessing that the vacuum valve on the controller is leaking/bad. Has anyone else experienced this issue?
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Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
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I learned a great deal about the air-con system in these cars when I upgraded mine.
first, I had to look at your profile to see what year car we are talking about.
I am very well versed in the 77 up switch. Not so much with the earlier version.
It doesn't really sound like a vacuum leak to the switch, but its possible.
The default position is to blow down as in the heater, floor vents. When your air stops blowing out the dash vents. Can you feel it blowing down by your right foot?
If so, you might be onto something.
If not. More likely your evaporator is icing up or blocked.
Your Profile says you have a 74. This factory would be a VIR system. Have you changed it over with a VIR eliminator kit?
Are you running R12 gas?
Answer these questions and I think I can walk you through the issue.
First. Does air blow on the floor when it stops coming out the center vents.
And other than a compressor, what other mods have you done?
first, I had to look at your profile to see what year car we are talking about.
I am very well versed in the 77 up switch. Not so much with the earlier version.
It doesn't really sound like a vacuum leak to the switch, but its possible.
The default position is to blow down as in the heater, floor vents. When your air stops blowing out the dash vents. Can you feel it blowing down by your right foot?
If so, you might be onto something.
If not. More likely your evaporator is icing up or blocked.
Your Profile says you have a 74. This factory would be a VIR system. Have you changed it over with a VIR eliminator kit?
Are you running R12 gas?
Answer these questions and I think I can walk you through the issue.
First. Does air blow on the floor when it stops coming out the center vents.
And other than a compressor, what other mods have you done?
Thread Starter
Intermediate
Joined: Aug 2023
Posts: 25
Likes: 28
From: Virginia
1974 is correct. The system is still stock and I did not delete the VIR. The only new part is the compressor and it is running R134 (pretty cold, too). I can feel it blowing down at my feet somewhat after it stops coming from the vents. No other direction works including the defrost when it is acting stupid. After stopping for a minute, I can get it to work in any position including defrost. Thank You for your help.
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Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
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The answer, somewhat. Concerns me. This sounds like, if it is indeed blowing down, as in a HVAC system leak. Then yes, you could indeed have a faulty vacuum switch. Vacuum switches generally leak all the time, or not at all. If you have a vacuum guage you could certainly test the system to see if it's holding vacuum.
if the amount of air seems to reduce after running for awhile, that sounds like blockage in the heater/evaporator box. Which is common. 50 years of leaves and junk getting down the vent on the right and blocking up the box.
Having really cold air with 134 and a VIR System sounds like a bloody miracle to me. But if it blows cold on a system that can not be adjusted for 134 gas. Well, good on ya!
but if vent control is lost. Yes, time to pull the map pocket (lower RH dash) and the console sides to gain access to the HVAC system. And start checking.
if air flow is reducing, time to pull the heater box apart and clean it out.
if the amount of air seems to reduce after running for awhile, that sounds like blockage in the heater/evaporator box. Which is common. 50 years of leaves and junk getting down the vent on the right and blocking up the box.
Having really cold air with 134 and a VIR System sounds like a bloody miracle to me. But if it blows cold on a system that can not be adjusted for 134 gas. Well, good on ya!
but if vent control is lost. Yes, time to pull the map pocket (lower RH dash) and the console sides to gain access to the HVAC system. And start checking.
if air flow is reducing, time to pull the heater box apart and clean it out.
Thread Starter
Intermediate
Joined: Aug 2023
Posts: 25
Likes: 28
From: Virginia
Thank You for the guidance. I am going to put a vacuum gauge on it and see what happens. I was just hoping that someone had experienced this issue before I started taking everything apart. And yes, I consider myself fortunate that the system blows cold with R134. I did not have high expectations, but I got lucky this time. This car has been funny like that- either things go easy and work well or it fights me every step of the way. You never know what you will get.
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Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
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Oh I understand! I've been a C3 owner for many years.
I tried running 134 in My VIR air-con system. I got kinda, sorta cold air. Worked really well in the winter. Not so much on a 90 degree day!
Converted my system. I have a how to thread on here.
Yes many have experienced what you are experiencing. The issue is there is more than one answer to the problem. Yes you are likely losing vacuum in your HVAC system. But there are a NUMBER of places that you can be leaking from. Throwing parts at it is foolish. No matter what fixed the other guys car.
Best to check it. Find the leak. Repair as necessary.
I tried running 134 in My VIR air-con system. I got kinda, sorta cold air. Worked really well in the winter. Not so much on a 90 degree day!
Converted my system. I have a how to thread on here.
Yes many have experienced what you are experiencing. The issue is there is more than one answer to the problem. Yes you are likely losing vacuum in your HVAC system. But there are a NUMBER of places that you can be leaking from. Throwing parts at it is foolish. No matter what fixed the other guys car.
Best to check it. Find the leak. Repair as necessary.
Le Mans Master
Joined: Jun 2019
Posts: 7,645
Likes: 2,464
From: Indiana
This link covers all the switches..
do not throw away the original switch!
https://www.corvetteforum.com/forums...-switch-2.html
do not throw away the original switch!
https://www.corvetteforum.com/forums...-switch-2.html
