Delayed AC Top Vent Output
Thread Starter
Team Owner
Joined: Sep 1999
Posts: 34,062
Likes: 4
From: Evans, GA
Delayed AC Top Vent Output
This is a 96, LT1, Coupe w/46kmiles. No previous problems.
Since the last 5 days the AC system waits from 2-3 minutes before air is present at at Instrument Panel Vents. This happens on both manual and on automatic and regardless of the output selection. The fan speed has been tried at each of the speed on manual and automatic.
Once the air is moving from the IP vents is comntinues to fuction OK untill you shut off the engine and restart; again the wait for the air. No messages on the display.
Also missing is the sound of the damper doors changing position behind the dash.
Any one solved this type problem or have any ideas about where to start to get a solution?????
Since the last 5 days the AC system waits from 2-3 minutes before air is present at at Instrument Panel Vents. This happens on both manual and on automatic and regardless of the output selection. The fan speed has been tried at each of the speed on manual and automatic.
Once the air is moving from the IP vents is comntinues to fuction OK untill you shut off the engine and restart; again the wait for the air. No messages on the display.
Also missing is the sound of the damper doors changing position behind the dash.
Any one solved this type problem or have any ideas about where to start to get a solution?????
Instructor
Joined: Apr 2002
Posts: 237
Likes: 0
From: KALAMAZOO MI
Re: Delayed AC Top Vent Output (1Patriot)
As I said on the other board, I am having the exact same problem!!! If I leave the a/c on for 3-4 minutes it shoots air thru the facia vents but for the first few minutes, the cold air comes out of the defroster and heater vents only. Very strange.... can someone help us???
Le Mans Master
Joined: May 1999
Posts: 6,514
Likes: 1,301
From: Windermere FL
Re: Delayed AC Top Vent Output (1Patriot)
I think we can narrow it down to two possible common causes. I would look at the easy one first:
1. There is a 'T' fitting that supplies vacuum from the engine to the A/C duCts. This 'T' is located near the rear of the engine (I think under the ruel rail covers on an LT-1). The 'T' is made out of plastic and has a tendency to melt with engine heat and develop a vacuum leak that will give you the symptoms you describe. Make sure to check the underside of the 'T' because this is where the heat really gets to it. Or just replace it, it is a cheap part
2. If you have C68, there is a tech tip that describes common problems with the controller https://www.corvetteforum.com/techti...D=92&TopicID=2
Good Luck!
1. There is a 'T' fitting that supplies vacuum from the engine to the A/C duCts. This 'T' is located near the rear of the engine (I think under the ruel rail covers on an LT-1). The 'T' is made out of plastic and has a tendency to melt with engine heat and develop a vacuum leak that will give you the symptoms you describe. Make sure to check the underside of the 'T' because this is where the heat really gets to it. Or just replace it, it is a cheap part
2. If you have C68, there is a tech tip that describes common problems with the controller https://www.corvetteforum.com/techti...D=92&TopicID=2
Good Luck!
Drifting
Joined: Jun 2001
Posts: 1,997
Likes: 1
From: Lake Ozark MO
Re: Delayed AC Top Vent Output (1Patriot)
On my '96 if the interior temp is very warm, it'll blast the cold air from the defrost vents until the interior temp cools down some and the fan shifts to a slower speed. Then the front vents will start to blow. If I park my car in the garage and then start the car at a later time, the A/C will blow directly from the front vents if the interior temp is cool enough.
It seems that GM didn't want to blast the air from the front vents. It only seems to switch (when in auto) after the fan speed slows from max.
I've checked the A/C for codes and found none. So I assume it's operating correctly. I haven't found any vacuum leaks at the typical spots either.
It seems that GM didn't want to blast the air from the front vents. It only seems to switch (when in auto) after the fan speed slows from max.
I've checked the A/C for codes and found none. So I assume it's operating correctly. I haven't found any vacuum leaks at the typical spots either.
Thread Starter
Team Owner
Joined: Sep 1999
Posts: 34,062
Likes: 4
From: Evans, GA
Re: Delayed AC Top Vent Output (Dan Parker '96)
Dan, Before the current condition, I had about a 30 second delay from engine start untill air was streaming from the IP venbts. Now it takes from 2-3 minutes. Even when the car is garaged.
Any more thoughts???
Any more thoughts???
