Jimmy W1

Once in a while after I drive my car 1/2 mile or so, I hear this thump. It sounds like a vent closing.

I don't use my AC. I drive with the Windows down, even when it's pretty hot out. Is there a vent that could be closing automatically? I have the temperature setting set on about 80 degrees.

Any thoughts?

Corvette_Ed

The only thump I hear in my car is from the two subs in my trunk. The only other sound I hear is the NPP exhaust when I stomp on the gas.

JohnR2000

From reading some of your posts, it sounds like you have an amazing stereo system. I'm also in DFW area so hope to run into you some day.
(Not actually run into you)

Jimmy W1

It's not a continuous thumping. It just does it one time when I first start out to go somewhere.

But it sounds like it is coming from inside the car. And it sounds exactly like a door on a vent switching or closing.

flyingbunnys

I know that you do not use A/C, but what about air from outside or recirculated air?


Could be the recirculation motor flap opening and closing?

bucwheat

It may be the NPP exhaust valve

wayback

It is the traction control system calibrating. Usually sounds like two thumps from the rear.
All 3 of my C6s have done this. It's normal.

Jimmy W1

I ran into a friend of mine at a cruise in Tuesday. He is retired from GM, owns about 5 or 6 Corvettes and is a judge at numerous shows. He said that it was probably the vent under the dash switching over- closing off the AC vent and opening the heat vent- since I have the both temperatures set on 83 degrees. Yesterday it did it about a minute after I started the car and I was loading some stuff in the back end.

I keep the temperature this high with the fan turned off because I always drive with the windows down and I don't want the AC running. I assume when the car engine shuts off and the car sits overnight, the AC vent will open. Then after I start it up and the heater is on, the vent is closing. But I am just assuming that is what it's doing.

Thanks for your comments. I appreciate it.

Jimmy W1

I thought this might be it when I read your reply, because my traction control emblem has been coming on quite a bit lately. I just hit the reset and after a few minutes it goes out. But I am sure that the sound is coming from under the dash and like I told my buddy Tuesday, it sounds exactly like the older cars did when you had the vent ***** under the dash and when you shut them they would make a "thump" sound.
Plus there's always just one thump sound. Never two.

FortMorganAl

4 thumps near the right rear tire a few minutes (I believe 4) after you start the engine would be the BCM computer opening and closing the vent solenoids in the fuel system to do a large leak test, small leak test, canister restriction vent test, and purge solenoid valve leak test. I hear them occasionally.

But if it is really inside the car and only one thump then I think your friend is right that it is the A/C. But you are wrong that you can shut off the A/C by just raising the temperature. The compressor runs all the time unless you manually turn it off with the button. And, no the vent/temperature control damper should not move overnight because it is operated by a motor, not vacuum. This isn't a '65 Corvette. But you may get a thump when it the HVAC computer commands the motor to move to a limit.