grantv

Every morning as I drive to work right around the same distance from home (about 1K or under a mile), I get what sounds like a muffled trap door shutting. It's not loud, sounds like it's coming from under the right front of the car.
It's so consistent I at first thought I was driving over something (manhole?) because generally the first K is the same route, but it's the same on other roads as well.
The AIR system is fully removed and tuned out; pump, all piping, vacuum source plugged...
Happens regardless if heating system is fully off (every morning right now) or on. Pretty sure it happens under accel, coast or decel. Anybody else get this? Ideas? Cooling system?

jcgunn

Sounds like one of the air diverter doors in the HVAC system. Search the forum on "Re-indexing HVAC"

ken90004

This is your flaps automatically adjusting once you reach a standard air speed. If this didn't happen, you're create a positive lift and end up flying to work. You may wish to keep your speed below 90 knots or 103 mph ground speed.

dadaroo

Normally there is one in every crowd. You just beat me to it.

Chicago1

Ill say it just because but you sure it's not the car automatically locking the doors..

grantv

Yep, sure. They lock at 15 or so, nice and quiet.
Gonna check the HVAC thing, but seems odd to me this would happen when the HVAC system is completely off.

k24556

Inside the car or outside? if outside, then sway bar links loose or bad would be the first place I look

grantv

Can't see that... happens once every morning only, at exactly the same distance from home. I need to try and record it. Assuming it's HVAC or cooling system related due to this.

Bill Curlee

When you actually operate your HVAC System,, are you able to operate the AIR level doors and all the air comes out of the PROPER doors/vents?

What HVAC System do you have??

Dual Climate Control or the manual operated system??

Turn the HVAC system ON and select a specific operating mode and temp. See if the noise still happens.

All of those ZONE doors and flaps are operated by engine VACUUM.

If you have a Dual Zone system, the TEMPERATURE DOORS are operated by electric actuator motors. They cycle and recalibrate them selves when the system is first operated.

BC

grantv

I'll try to chase this down over the next few days with everyone's ideas in mind.
Will start with turning on the AC and seeing if all vents blow air where they should, then change some settings to see if I hear anything similar. Keep in mind this happens every morning, with the system completely off.
I have dual zone.
Pretty sure I only hear this in the morning, which at this point (cool end of August this year) the system is completely off. I hear no odd noises when I turn on my AC after work, even if I change from high vents to all vents or vice versa.

grantv

Well, pretty sure the flap sound still happened with the system on, but you opened my eyes to the fact that my zone system does not work! I'm only pretty sure as I sat beside the road for a few minutes this morning with the car running while I was playing with the controls, so the flap sound occurred a few blocks early (yes, it's that consistent).
I have the dual climate controls. Yesterday I tried on the way home to vary temps left to right with AC on. Didn't seem to be any different even if I swung the PS side to full heat. Didn't try with AC off yet.
This morning on the way to work checked out all the zones. I have 1 zone; all of them.
Pick floor only; all vents.
Pick dash only; all vents
Didn't try with the defrost as that turns the AC on.
No sounds when I change zones at all.

Safe to assume I have a vacuum leak on the line going to the heating system I guess? Or at least that's the best place to start looking for an issue? I have an old vacuum tester, what vacuum should I read and where should I hit the lines? Any pictures of where the vacuum line goes to the heating system?
A lot of questions, and pushing my luck, I know...

Bill Curlee

LOL! That's what I thought was going to be wrong. WELL,,,,,, It starts with a very small nylon vacuum line fitting on the BACK of the intake manifold. VERY difficult to get to and or work on. You really need to remove the intake manifold to properly access it:

OEM line and fitting:





The OEM vacuum line is too short and very difficult to work with. I lengthened mine to make it easier:






Here is where it enters the main wire harness to get down to the reservoir tank in the passengers fender well:






Fender well tank and connections (labeled)




IF,,, the vacuum line inside that harness (under the battery) is or was ever exposed to battery acid,,, its TOAST and needs to be replaced. Acid eats it away.

Just for knowledge, here is HVAC Air Box and the Damper Door ZONE controller and all the little fancy colored vacuum lines and damper vacuum servos on the air box. The PURPLE line on the controller is the vacuum supply for the system:



Vacuum actuator & below the actuator is the TEMPERATURE DOOR ELECTRIC ACTUATOR for the passengers side:



Drivers side actuators and vacuum servo:




Pull up the DTCs using the DIC and see if you have ANY HVAC System DTCs. If you do,, clear them and see if you can get the actuators to CYCLE through their SELF TEST.

Bill

ken90004

great photos. MY driver side air blend door (actuator) needs replaced. I'm getting a HVAC code that had something to do with the flaps not traveling the correct distance


I read a post about pulling a fuse in the box under the passengers side foot wheel. That re-synced something. I had cool air blowing from the drivers side for a day, and now it is back to warm air.


I guess there is a plastic gear that doesn't hold up well.


I'm going to run it out to the dealership and have them replace it.


But this was easy to figure out something was wrong. I mean cold/hot air didn't come out of the driver's side vents according to what the temp was set.

grantv

I was hoping for a more thorough answer...
Seriously, great stuff Bill! Wow!

The only code I have for the HVAC is a history B0361H which I found indicates "Left actuator feedback short to GRD".
I'm assuming my problem goes back to a vacuum leak, correct? I'll try and get behind the manifold on the long weekend, if not I'll deal with this oddity as is until winter, make this a project for then while it's off the road.

grantv

So this past weekend I finally got tired of not being able to control my zones. It IS very tight getting back there behind the manifold in any way with average man hands or a phone (camera).
It went something like this:
-Turn on video cam on old (non-connected) phone (for light and to help see what I've done)
-Point it in there, can see hose is somewhat loose on manifold connection (likely loosened when I snipped the AIR hose back there and tried to no end to twist/drag it out. No, I never did get the entire AIR hose out).
-Reach my hand in there, push it just lightly back on (can't really grab the hose).
-Camera in there; confirm it's on, yes
-Get hand in there to try and push on better. Flip it off instead.
-Camera to confirm I just messed up. Yes.
-Hand back in there, barely get it back on...
Well, you can repeat the last 3 steps about 10 times! GRRR. It's on enough to give me control, but I'm sure it will loosen up again. I need a female to get their hand in there for me (wife, niece, somebody...).

73Corvette

I love your play by play... I know it's not funny, buy you have a great attitude about it...
Bill... many of us feel our "hose" is too short, glad you were able to make yours longer

dadaroo

You may just have to remove the manifold and make sure you have a good vacuum line connection. You can make it long enough to connect it all up where you have good access. Removing the manifold is not that hard. I would recommend a new gasket set to seal it all back up.


Mr. Sam

grantv

It is funny to me. And thanks.
My dad always said; if you can't laugh at yourself don't laugh at anybody else. I do the former when necessary (looking back at fixing the darn vacuum hose and scuffing my hands up for example...), try not to do the latter.
I did think of 2 possible fixes without removing the manifold (I do not really want to) in case anybody else is in the same position.
1 - Find a person with small arms/hands who is willing to get a tiny bit dirty. This is what I will try this coming weekend. My nieces are all pretty small.
2 - Run a loop. I am able to reach the hose and carefully pull it back a little. And I can kind of get a straight line to the nozzle... so find a piece of rigid tubing same size as hard flex tube around 4" long, use a piece of flex tube at the end to push onto the nozzle (this end would have to be fixed or it might slip), and another flex around 8-10" long at the other end. This would fix the problem without removing the manifold (end result; I would also have a longer hose).

73Corvette

Looks like a plan... Nice diagram...