Mildew in AC ducts???

Rockrz · Post by **Rockrz** » Mon Jun 08, 2009 7:34 pm

I've noticed lately that when I first start up my truck and crank
up the AC, there's this kinda musty smell that comes out for
the first few seconds and then goes away.

It's not really a bad smell, but it's not something I've noticed
in other vehicles either. My wife's '04 Cavalier doesn't have it.

Is it possible that there could be a little bit of mildew down
inside the ducts somewhere?

If so, is there anyway to clean this out without taking
the entire dash apart to get into all the ducts?

Post by **HenryJ** » Mon Jun 08, 2009 7:43 pm

Water leak on floor

HenryJ wrote:The right or left plenum drain may be plugged or the drain has excess sealer that acts as a dam. Remove the obstruction or trim away excess sealer leaving no higher than 6.35 mm (1/4 in) to the bottom edge of the drain.

Water may enter through the air box if the air box is loose. If the air box is loose, tighten the lower right fastener first, then the other fasteners in a clockwise order (lower right, lower left, upper left, upper right) to 10 N·m (89 lb in).
The air box may have excess sealer causing interference and not allowing the air box to seat properly. If the air box cannot be seated properly against the front of dash due to an interference from the sealer, cut away excess sealer in order to allow a proper seal.

Max A/C is turned on through a car wash or heavy rain. Max A/C opens the recirculation/air box door (upward) in the air box. Water can pool on the door and gain entry to the front passenger compartment. Excess water can enter through the cowl grill fasteners and drop onto an open air box door, or splash onto the door from the plenum. It is sometimes possible to minimize the amount of water gaining access to the door by applying thumb grade sealer to the right most cowl grille fastener and the upper fender bolt holes before securing.

The inside of the plenum along the hinge pillar may have a void in the sealer. Inspect for voids outside the plenum along the hinge pillar. Clean the area and seal.

Rockrz · Post by **Rockrz** » Mon Jun 08, 2009 7:53 pm

Well, there's no wetness or moisture on the floor of any kind...
so I guess I need to check the seal around the air box?

Any pictures of any of this posted anywhere that you know of?

Rockrz · Post by **Rockrz** » Mon Jun 08, 2009 7:56 pm

I got it, first thing to check is the drainage
from the underside

Post by **HenryJ** » Mon Jun 08, 2009 8:00 pm

I would inspect the cowl opening after removing the cowl vent cover behind the hood.

Rockrz · Post by **Rockrz** » Mon Jun 08, 2009 8:07 pm

OK, so I'm looking for a bad gasket?

If so, is this something I can fix with that
make-a-gasket stuff in a tube?

I also remember seeing vehicles that had
their air box drain clogged causing moisture
to collect up inside, so I'll check that with
a coathanger (???) gently to make sure
there's no obstruction there

Post by **HenryJ** » Mon Jun 08, 2009 8:16 pm

Rockrz wrote:OK, so I'm looking for a bad gasket?

Not really. That will just let it leak on the floor. You are looking for the dam and a plugged drain.

Rockrz · Post by **Rockrz** » Tue Jun 09, 2009 9:20 am

OK, I'll remove the cowl and see what I can find
by way of blocked passages

killian96ss · Post by **killian96ss** » Tue Jun 09, 2009 11:41 am

GM used to make a spray to get rid of the moldy smell. You just spray it into the air openings in the cowl to get rid of the smell.

Steve

Post by **HenryJ** » Tue Jun 09, 2009 11:58 am

"Febrese" might do it too?

First stop the source.

Rockrz · Post by **Rockrz** » Tue Jun 09, 2009 2:11 pm

HenryJ wrote:First stop the source.

When I have time this weekend, I'm going to take
the cowl off and see if it's stopped up

I assume there is some sort of drain inside there
I'm looking for?

And, I'll make sure the drain from the underside
of the truck is clear.

Post by **HenryJ** » Tue Jun 09, 2009 2:48 pm

The drain is at the bottom. You are looking for the dam. The problem as to why water is entering the door instead of running down to the drain.
Then check both the cowl drain and the HVAC drain.

Rockrz · Post by **Rockrz** » Sat Jun 27, 2009 8:19 pm

Well, I crawled under the truck today and I can't see where there's a drain on the underside.

I remember seeing vehicles having what looked like a hose coming down over on the passenger side that you could get a coathanger up into to make sure there were no restrictions.

Is this what I'm supposed to be looking for on the underside?
(HVAC drain?)

Rockrz · Post by **Rockrz** » Wed Jul 01, 2009 8:05 am

OK, I'll crawl up under there and look again.
Maybe I missed it.

It's not inside the fender well where that
has to be removed to see it, is it?

04crewvt · Post by **04crewvt** » Wed Jul 01, 2009 8:25 am

For cleaning out the mildew/smell check with an A/C repair place, I have used some great stuff for cleaning and deodorizing A/C units a tech gave me once. No idea what it was called.

Rockrz · Post by **Rockrz** » Wed Jul 01, 2009 8:35 am

Wouldn't I need to make sure there's no restrictions first, and
if there are then clear them so this doesn't happen again?

04crewvt · Post by **04crewvt** » Wed Jul 01, 2009 8:45 am

yup this is just to clean the smell and kill the mold/mildew once the drains are unplugged. It is typical for the drains on window A/C units to plug up and once they start having water back up in them the problems start. The guys would come in clear the vents thenspray this stuff in and run the unit.

Rockrz · Post by **Rockrz** » Sat Jul 04, 2009 6:31 pm

Found a service bulletin for this....

Reckon this would be covered under some sort of recall?
If not, it oughtta be. "Microbial growth" can't be good
for your health you know...

Here's the info I found:

Bulletin No.: 99-01-39-004B

Date: May 29, 2007

TECHNICAL

Subject:
Air Conditioning Odor (Install Evaporator Core Dryer Kit and Apply Cooling Coil Coating)

Models:
1993-2008 GM Passenger Cars and Trucks (Including Saturn)
2008 and Prior HUMMER H2, H3

All Equipped with Air Conditioning

Supercede:

This bulletin is being revised to update the vehicle applications, model years, correction procedure, parts information and tool numbers. Please discard Corporate Bulletin Number 99-01-39-004A (Section 01 - HVAC).

Condition

Some customers may comment about musty odors emitted from the Heating, Ventilation and Air Conditioning (HVAC) system at vehicle start-up in hot, humid conditions.

Cause

This condition may be caused by condensate build-up on the evaporator core, which does not evaporate by itself in high humidity conditions. The odor may be the result of microbial growth on the evaporator core. When the blower motor fan is turned on, the microbial growth may release an unpleasant musty odor into the passenger compartment.

There are several other possible sources of a musty odor in a vehicle. A common source is a water leak into the interior of the vehicle or foreign material in the HVAC air distribution system. Follow the procedures in SI for identifying and correcting water leaks and air inlet inspection.

The procedure contained in this bulletin is only applicable if the odor source has been determined to be microbial growth on the evaporator core inside the HVAC module.

Correction

Many vehicles currently incorporate an afterblow function within the HVAC control module software. The afterblow feature, when enabled, employs the HVAC blower fan to dry the evaporator after vehicle shut down and this function will inhibit microbial growth. Technicians are to confirm that the customer concern is evaporator core odor and that the vehicle has the imbedded afterblow feature, as defined in the SI document for that specific vehicle model, model year and specific HVAC option. Refer to SI for enabling the afterblow function. Vehicles being delivered in areas prone to high humidity conditions may benefit from having the afterblow enabled calibration installed prior to any customer comment.

If the vehicle is not factory equipped with the imbedded afterblow enable feature, it may be added with the Electronic Evaporator Dryer Module Kit (P/N 12497910 or AC Delco 15-5876).

When installing the Electronic Evaporator Dryer Module, you MUST use the included electrical splice connectors to ensure a proper splice. Complete detailed installation instructions and self testing procedures are supplied with the kit. If necessary, the Electronic Evaporator Dryer Module may be installed underhood if it is protected from extreme heat and water splash areas.

To immediately remove the evaporator core odor on all suspect vehicles, it is necessary to eliminate the microbial growth and prevent its re-occurrence. To accomplish this, perform the following procedure:

Vehicle and Applicator Tool Preparation

The evaporator core must be dry . This may be accomplished by disabling the compressor and running the blower fan on the recirc heat setting for an extended period of time.

Note: Compressor engagement will cause the evaporator core to remain wet and will prevent full adherence of the Coiling Coil Coating to the evaporator core surfaces.

Verify that the air conditioning drain hose is not clogged and place a drain pan beneath the vehicle. Place a protective cover over the carpet below the evaporator core.

Remove the cabin air filter, if equipped, and cover the opening prior to applying the Cooling Coil Coating, as the product may clog the filter. If the cabin air filter appears to have little or no remaining life, suggest a replacement to your customer.

If the HVAC module has a blower motor cooling tube, be careful NOT TO SPRAY THE COOLING COIL COATING INTO THE BLOWER MOTOR COOLING TUBE.

Attach the Flexible Applicator Pressure Spray Tool (J-43810-20A) to a compressed air line operating at 586 kPa (85 psi) to 793 kPa (115 psi).

Shake the bottle of Cooling Coil Coating well. Screw the bottle onto the cap on the applicator tools pick-up tube.

NOTE: The pick-up tube is designed for 120 ml (4 oz) and 240 ml (8 oz) bottles and should coil slightly in the bottom of a 120 ml (4 oz) bottle.

Use one of the following three methods to apply the Cooling Coil Coating.

If the Pressure Applicator Spray Tool (J-43810-20A) is not available, the Cooling Coil Coating is also available in an aerosol can (P/N 12377951 (in Canada, 10953503)).

Application Through Blower Motor Control Module Opening

Remove the blower motor control module (blower motor resistor). Refer to the applicable procedure in SI.

Clean any debris or foreign material from inside the HVAC module and on the evaporator core surface.

Apply the Cooling Coil Coating directly to the evaporator core through the blower motor blower motor control module (blower motor resistor) opening.

Use the flexible wand to direct the Cooling Coil Coating over the entire evaporator core and surrounding gasket surfaces.

When the application is complete, install the blower motor blower motor control module (blower motor control module).

Application Through Blower Motor Opening

Remove the blower motor. Refer to the applicable blower motor removal procedure in SI.

Clean any debris or foreign material from inside the HVAC module and on the evaporator core surface.

Apply the Cooling Coil Coating directly to the evaporator core through the blower motor opening.

Use the flexible wand to direct the Cooling Coil Coating over the entire evaporator core and surrounding gasket surfaces.

When the application is complete, install the blower motor.

Application Through a Hole in the HVAC Module

If neither of the two previous application methods are available, it may be necessary to drill a hole in the HVAC module.

Locate an area of the HVAC module between the blower motor and the evaporator core. Drill a 10 mm (3/8 in) hole in the HVAC module. Use caution to keep the drill clear of the evaporator core and the blower motor fan.

With the air distribution vents closed and the blower motor fan speed on HIGH, insert the applicator tool into the hole and spray the Cooling Coil Coating into the airstream toward the evaporator core.

Use a GM approved RTV sealant to plug the hole in the HVAC module.

After the Cooling Coil Coating application is complete, start and run the vehicle for approximately 10 minutes, with the compressor disabled, HVAC mode set to Recirculate/Max, heat set to full warm, blower motor fan speed on high, and one window open approximately 12 mm (1/2 in). This cures the Cooling Coil Coating onto the evaporator core surface.

While the engine is running, rinse the applicator tool with warm water to prolong the life of the tool. Be sure to spray warm water through the nozzle to rinse out any residual Cooling Coil Coating still in the capillary pick up tube, otherwise it will dry and clog the applicator tool. Also remove the small green valve from the bottle cap and rinse it thoroughly while rolling it between two fingers and then reinstall it. If this valve is clogged the Cooling Coil Coating will not flow through the applicator tool.

Shut off the engine and enable the compressor again.

Verify proper HVAC system operation.

Remove the protective cover from inside the vehicle.

Remove the drain pan from underneath the vehicle.

Reinstall the cabin air filter if necessary.

Rockrz · Post by **Rockrz** » Sun Jul 12, 2009 7:19 pm

I'm just gonna drill me a hole on the evaporator core cover
and spray a mixture of bleach and water all over inside onto the
evaporator core and then follow that with some Lysol to make
sure all the microbial growth is dead

The, cover the hole I drilled with a rubber gromment in case
I ever have to do this again I'll have easy access. (I read on
another board where this is what some folks did and it worked)

Thanks!