Uncomfortable Cold Air Draft

[Sierra89]

Hi all,

For a few winters now our 2002 Tahoe has had an issue during the winter months with cold air blowing in on the passengers feet. It comes in very strong from around the blower motor under the glove box while driving. It gets stronger the faster the truck is driven. It gets less when the fan is turned up, and it also gets less when the recirculation button is pressed. But when the defrost is on I can't have the recirculation button pressed and its very uncomfortable for the passenger because of the cold. Anyone had a similar problem? I've tried to find a source of the cold air but have had no luck.

THanks

[sonjaab]

Its sorta a throwback to the old "astro ventilation" days from GM to keep fresh air flowing thru the passenger cabin. When your moving the air will pass thru the cabin unless the HVAC is set and running in the re-circ or defrost mode.

Some GM models the fan also never totally shuts off either.

 

My Dakota pickup has NO air flow if the fan is shut off unlike the GMs.

[oldmann]

I always thought it was funny that my 800 let air through the vents when the hvac was off.

[jdewolfe]

My dad's 01 2500HD does this horribly as well. Driver is sweating and the passenger is freezing. I hate riding in that truck in the winter because of it. My 06 definitely does not have this issue.

[titanium10k]

Sounds like your recirculation actuator failed. You should be able to drive down the road, place the setting on front vents and put in recirc mode. There should be no airflow with the fan off. If it failed I was able to remove mine on my 02 by removing the glove box and put a coat hanger to hold the door shut. Ac works better and I don't smell the stinky exhaust from the car ahead of me.

[KMGZ400]

my 2001 has this problem... except its lke coming from the cracks around the cupholders... its not strong, just w kinda annoying

[Sierra89]

Age old problem for the GMT800's. Search for the TSB. Blend door/actuator issue.

 

Thanks everyone for your thoughts, I'll be looking into this. My Girlfriend bought a 06 Sierra Z71 a few months ago and I noticed that it does the same thing but nowhere near as bad as the old Hoe. That kinda told me that this may be a GMT800 issue. Were heading down to Lake Placid and while we are there it is forecast to be around -20f. So we'll see hot the Sierra does!

[PhilB]

The TSB number is #01-01-37-008. Do a search on that number and you will find the verbiage for the TSB.

[sonjaab]

Sorry to say there is NO cure for the unwanted airflow!

 

All 3 of my GMT-800s did it and my 07 gmt-900 does it also

along with my 07 Cadillac !

 

The only way to stop the "cold feet draft" is to select the a/c

in the Recirc mode or defroster setting (auto recirc is automatic

when defrost is used).

Not a real cure as the fan must be on for the mode/recirc to engage the air blend door.......................

There is no real OFF setting !

 

Like I posted on my Dakota truck if the fan is OFF there is NO

airflow of any kind no matter what HVAC setting!

 

Any hints????????????

[BlackSilver]

My 01 1500 had the problem. Caused by a bad installation of some under-dash air passages, with a crushed gasket if I recall.

 

Dealer fixed it under warranty, and it wasn't hard to do. See if you can track down the TSB.

[PhilB]

Here is the verbiage for TSB #01-01-37-008

 

Heating, A/C - Passenger Side of Vehicle Colder/Warmer

 

File In Section: 01 - HVAC

 

Bulletin No.: 01-01-37-008

 

Date: April, 2001

 

TECHNICAL

 

Subject:

Passenger Side of Vehicle Colder/Warmer Than Driver's Side

(Repair HVAC Case to Cowl Seal)

 

Models:

1999-2001 Chevrolet and GMC C/K Pickup (Silverado, Sierra) and Utility (Suburban, Tahoe, Yukon, Yukon XL) Models

2002 Cadillac Escalade

 

Condition

 

Some customers may comment that the passenger side of the vehicle may be:

 

1. Colder than the driver's side when the heat mode is on.

 

2. Warmer than the driver's side when the air conditioning (A/C) mode is on.

 

3. There may be dampness on the vehicle dash assembly when the A/C mode is on.

 

 

Cause

 

Condition may be due to poor sealing of the HVAC air inlet case to the front of dash or the recirculation mode door actuator may not hold the recirculation door closed while driving.

 

Correction

 

Replace the recirculation door actuator (if necessary) and repair the HVAC case to cowl seal using the following procedures:

 

1. Place the A/C control in the manual heat mode.

 

2. Remove the fixed mast radio antenna.

 

3. Open the hood and install fender covers.

 

4. Remove both wiper arm assemblies using the following procedure:

 

4.1. Disconnect the washer solvent hose from the air inlet grille panel nozzle.

 

4.2. Remove the cover from the wiper arm retainer. Remove the retainer.

 

 

Important: Use a battery terminal puller in order to remove the wiper arm.

 

Rock the wiper arm back and forth in order to loosen the arm from the drive shaft. Remove the wiper arm.

 

5. Lower the hood.

 

6. Remove the air inlet grille panel using the following procedure:

 

6.1. On each end of the air inlet grille panel is a rubber flap for the hood hinge cutout. Lift this flap and remove the air inlet grille panel attaching screw.

 

6.2. Remove the air inlet grille panel center top push pin.

 

6.3. Remove the clips that position the forward edge of the grille panel to the top of the cowl.

 

6.4. Disconnect the windshield washer supply hose from the bottom of the grille panel.

 

6.5. Remove the air inlet grille panel by sliding the panel rearward up the windshield and out.

 

 

7. Just to the left of the right hood hinge, on the horizontal surface of the cowl, locate a cover that is sealed in place. The cover has TRW stamped into it.

 

8. With a sharp knife, cut out the panel following the panel impression in the sealer tape.

 

9. Place a lifting device between the cover and the dash. Lift the cover enough to allow another tool to depress and release the front retaining tabs by pushing rearward on them. Remove the cover.

 

10. Look through the opening where you just removed the cover. You will see what looks like a piece of foam about 76 x 127 mm (3 x 5 in). This is the A/C recirculation door that is within the HVAC module.

 

11. Reach into the opening and carefully pull on the air inlet recirculation door. If the recirculation door moves with very little effort, replace the air inlet (recirculation) door actuator (Manual systems only). For systems with the Automatic Temperature control, initialize the system using published Service procedures.

 

12. Between the top of the HVAC air inlet module (appears as a 6 mm (1/4 inch) black strip) and the cowl sheet metal is a foam seal. This foam seal may be improperly positioned or damaged in some way (insufficient crush/sealing). This may allow outside ambient air to enter the passenger compartment incorrectly (under driving conditions). This can be corrected using the following procedure:

 

Important: It is imperative that a good seal be achieved over the entire surface areas (no voids or skips), especially around the rear and sides of the HVAC case to cowl areas.

 

12.1. Seal the area between the cowl and HVAC case with RTV Silicone Rubber Sealant, P/N 12345739 (in Canada, use P/N 10953541).

 

12.2. Using your finger, from the engine side of the cowl, ensure that the foam is stuck nicely to the HVAC module and does not have any distortions.

 

12.3. From the engine side of the cowl, working through the opening in the horizontal surface of the cowl, place a shop cloth into the opening and cover the blower fan. This keeps silicone from dripping onto the motor and causing an imbalance condition.

 

12.4. From the engine side of the cowl, working through the opening in the horizontal surface of the cowl, apply the RTV silicone to bridge the gap and cover the foam between the cowl sheet metal and the HVAC module case. Inspect your work with a light and a mirror. Ensure that no gaps or skips are present in the RTV seal.

 

12.5. Inspect your work for potential drips, runs, etc. If no problem is seen, remove the shop cloth covering the blower motor.

 

13. Apply a 3 mm (1/8 in) bead of weatherstrip adhesive, P/N 12345097 (in Canada, use P/N 10953479) around the opening in the horizontal surface of the cowl, where the cover fits into the cowl.

 

14. Place the cover on the workbench, top on the surface, and apply a 3 mm (1/8 in) bead of weatherstrip adhesive on the edge of the cover.

 

15. Place the cover into the cowl opening and snap into place.

 

16. Apply another bead of weatherstrip adhesive around the joint between the cover and the top of the cowl. Smooth this bead into a smooth surface with a finger or tool of some kind.

 

17. Place the leaf screen to the cowl. Attach the washer supply hose to the bottom of the air inlet grille panel. Do not place the fasteners in at this time.

 

18. Install the radio fixed mast antenna. Tighten 1/4 turn after contact is made with the base.

 

19. Lower but do not close the hood.

 

20. Center the opening in the air inlet grille panel around the antenna mast and then install the air inlet grille panel retaining screws.

 

Tighten

 

Tighten the screws to 2 Nm (18 lb in).

 

21. Raise the hood.

 

22. Reinstall the air inlet grille panel center retainer and front edge retaining clips.

 

23. Cycle the wipers to ensure the wiper system is in the parked position.

 

Important: Inspect the windshield lower edge on each side. About 51-76 mm (2-3 in) from the bottom, you will find a 13 mm (1/2 in) long black mark embedded in the glass. The black line is the position for the wiper blade to be in when the wiper system is in the parked position.

 

24. Install the wiper arm assemblies. Position the wiper blades just below the black marks in the windshield.

 

25. Install the retaining nuts.

 

Tighten

 

Tighten the retainers to 25 Nm (18 lb ft).

 

26. Reconnect the washer hoses.

 

27. Remove the fender covers.

 

28. Close the hood.

[Sierra89]

I started poking around under the dash and I found a bunch of broken black plastic bits , one piece looked almost like a broken Afro pick?? I'll tackle the TSB soon. The bad insulation on the firewall sounds like the source of the draft.