First start of the day, or if the car has been sitting in a hot parking lot for a long time, the odor coming out of the vents is sour, almost obnoxiuous!
Did a search on the subject, and Read Bill Curlee's Sticky thread on leaks (well done Bill, thanks!!).....I can honestly say, that is not the issue, also found and cleaned all the cowl drains of minimal trash. The A/C Evaporator drain is not clogged and drains well when in use.
Today I sprayed Ozium into the Cowl intake with the Blower and heater on high, used half the darn can! Figured this was a good way to "cook" the moisture out of the evaporator. Will have to see, er, smell in the morning to determine if it works.
Anyone else having this issue? What works/worked for you?

 

You sure something didn't die in there? Seriously, if it stinks that bad I'd be fearful of a dead mouse or something in your ducts.

 

Other than Disassembling the HVAC, I couldn't say without a doubt, that couldn't be the problem....I might also be overstating the degree of stink, it smells sour, not like roadkill.

 

Do you drive with the system on recirculate alot? I've found that leaving the intake on fresh air reduces the amount of moisture and no smells.

 

Ozium is good stuff, I hope it does the trick. I mentioned the rodent possibility only because I had that problem with my wife's Honda. They hadn't died in there but I found them nesting under the hood, and the smell was finding it's way into the car.

 

RedSoxVette could be on to something. I was doing a repair on my HVAC system where I had to remove the HVAC blower. When I took the blower out, to my surprise, I found pieces of corn, seeds, and yes, mouse hair. I was so surprized, I took a picture,



Fortunately, whatever decided to live there had moved on, but for some reason, HVAC ducting in our beloved C5's seem to make great mouse habitats. It is not to terrible to take the blower out.. I'd say it can be done in under ten minutes... it might be worth doing.

 

Drop the passenger side panel, the fan is right underneath and held in by three of four bolts. You may find a mouse nest in there. My friend had smells and we dropped it and found 5 baby mice dead from spinning in the fan. Access from the outside for mice is very easy.

 

I think a musty smell is a common problem. Mine has it when first turned on. There have been threads on this. Most suggest cleaning and unplugging the drain udders under the hood.

 

Your smell may be worse than this, but.....ever since I had my first car with factory A/C in 1974, I always prematurely shut off the A/C compressor about 5 minutes or so prior to arriving at my destination. This allows the A/C cooling unit in your car to warm and dry out (depending on the "relative humidity" in the atmosphere). Other than a mouse or other sources, I have ALWAYS had a fresh smelling system, the "recirculate" setting is also another source as fresh outside air will keep stale smells at a minimum. If you do need to use the "recirculate" feature, then disengage it at the same time you are disengaging the A/C compressor (pushing the "snowflake A/C" button and turning off the light).

 

I too have a musty smell, not road kill, but musty expecially on recirculate. Had the blower out about 8 months ago when my control module went bad and didn't see anything in the duct. I saw somewhere a thread showing the drilling of a small hole in the ducting and spraying in some GM solution to potentailly kill any mold or fungus which might have formed in the evaporator coil. Think there is a TSB on this. Has anyone done this (without drilling right into the evap coil) or tried other means short if disassembling the ductwork? How about Lysol or some other bleach laden spray? BIGHANK

 

There is a TSB out on this. GM has a kit which runs the HVAC fan after you turn off ignition to dry out the system so mold does not grow.

I have sucessfully used foaming cleaners on my other cars.

Here is the TSB:

Document ID# 798948
1998 Chevrolet/Geo Corvette


--------------------------------------------------------------------------------

Air Conditioning Odor (Install Kit) #99-01-39-004A - (May 22, 2001)
Air Conditioning Odor (Install Kit)
1993-2002 Passenger Cars

1993-2002 Light & Medium Duty Trucks

This bulletin is being revised to update the model years, service procedure, parts information and to add the GEO and Medium Duty models. Please discard Corporate Bulletin Number 99-01-39-004 (Section 01 - HVAC).

Condition
Some customers may comment on odors emitted from the air conditioning system, primarily at start-up in hot humid climates.

Cause
This 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. Follow the Service Manual procedure for identifying and correcting water leaks if other odor sources are found. The procedure contained in this bulletin is only applicable if the source of the odor has already been determined to be the HVAC module.

Correction
To remove odors of this type, it is necessary to eliminate the microbial growth and prevent its reoccurrence. To accomplish this, the following steps must be completed:

Apply evaporator core Cooling Coil Coating (Aerosol 6 oz), P/N 12377951 (AC Delco® 15-102) (in Canada, use P/N 10953503) or Cooling Coil Coating Kit with Extension Nozzle, P/N 12346391 (AC Delco® 10-120). Refills are available for the Cooling Coil Coating Kit with Extension Nozzle, P/N 12346391 (AC Delco® 10-120). Refer to the chart below.
Install the Electronic Evaporator Dryer, P/N 12497910 (AC Delco® 15-5876).

Important
The Cooling Coil Coatings listed above are the only GM approved products for the disinfection and long-term control of evaporator microbial growth.


The Cooling Coil Coating will disinfect the evaporator core and help inhibit the growth of future mold and mildew.

The Electronic Evaporator Dryer will activate when the ambient temperature near the module is above 16° C (60° F) when the vehicle is started up. Approximately 30 minutes after the vehicle has been turned off, the blower will activate for 10 seconds every 10 minutes for 2 hours unless the vehicle is restarted. If a restart occurs, the Electronic Evaporator Dryer module will reset automatically. This on/off blower activation will dry the evaporator core and case reducing the chance of reoccurring A/C odor. The Electronic Evaporator Dryer is self fused and has a battery rundown protection feature that inactivates the dryer if voltage drops below 12.5 volts.

Service Procedure
Visually inspect the air conditioning evaporator drain hose for obstructions and/or working condition.
The cooling coil coating fluid must be applied to a dry evaporator core. Apply coil coating fluid as described in the instructions supplied with the kit. In some instances, the blower motor resistor can be removed for this spraying operation. If used, the opening can be taped over and the nozzle inserted through a hole in the tape. The kit instructions identify a drilling procedure to apply the coating fluid. When using this type of procedure, care must be taken to avoid evaporator damage and any holes must be properly sealed. Some coating fluid may overflow from the drain hose.

Important
When installing the Electronic Evaporator Module, you MUST use the included electrical splice connectors to ensure a proper splice.


Complete detailed installation instructions and wire connectors are supplied with the Electronic Evaporator Dryer. The ground wire should be attached to a body ground source. If any other wire splicing procedures are needed, follow the wire repair procedures in the Electrical sub-section of Body & Accessories in the appropriate Service Manual. If required, the evaporator dryer can be installed underhood away from extreme heat conditions (i.e. exhaust manifolds) and/or water splash areas. In all cases, the evaporator dryer module must be secured with a Velcro® strip (not included in the kit), or you may use the integral hooks to utilize tie straps. Using a Velcro® strip is preferred as the use of the integral hooks may cause rattles.
When the installation procedure is complete and power is supplied, the module will self-test. Thirty seconds after power is supplied, the high blower speed will be activated 3 times (for 2 seconds per cycle). When the test has run, install the Electronic Evaporator Dryer label on the blower motor case in a visible area.
Parts Information
Part Number
Description

12377951

(AC Delco® 15-102)
Cooling Coil Coating (Aerosol 6 oz)

12346391

(AC Delco® 10-120)
Cooling Coil Coating Kit w/Extention Nozzle

12346390

(AC Delco® 10-121)
Refill for Cooling Coil Coating Kit

12497910

(AC Delco® 15-5876)
Electronic Evaporator Dryer Module Kit


Parts are expected to be available from GMSPO, 6/4/01.

Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

D3316
Apply Cooling Coil Coating/Install Electronic Evaporator Dryer
0.8 hr

 

moldy maybe? is yoru car leaking water when the a/c is on.. if not the drain could be plugged ... who knows what plugged it... now water and other debre are just sitting there 24/7 trying to creat life... wonderful isn't it?????


the drain is usually located on the firewall on the pass. side. I've not had a problem with mine yet so i can't confirm it's location... if you find it take a coat hanger and poke it... this will dislodge the plug and everything will come flushing out.. you might have to continue to unplug it until it's clean and clear. This does happen and is common among most cars. Good luck on your quest

then again maybe something died in there..

 

There are 3 RUBBER UDDERS (like drain hoses but rounded and split in half at the bottom. One each side of the car near the firewall and I think the 3rd is drivers side maybe a foot or so from the fender. These drains do get clogged with leaves and other junk. Clean em all out. Mine are clean but I am still geting the musty oder w/ac on. Feel that my evaporator needs a disinfecting. BIGHANK

 

Yea, my first post mentions all the cowl drains(udders) are clean...I'm thinking the same thing about disinfecting the evapotator

 

Over the course of a week, I've given the cowl vent about 4 good doses of Ozium with the fan set on High....so far it seems a little better, kinda like Ozium sented Urine....Yuck!!
I plan on replacing the dashpad soon and will disassemble and clean as much of the HVAC system as possible.

I purchased this car in February and the smell didn't start till the weather got hot and humid.