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A/c, comes on while car is not running

15K views 21 replies 10 participants last post by  greenman 
#1 ·
Hey peeps, was wondering if anyone else is running into this. I have noticed that when i get back in my car after driving some place that alot of air is blowing out of the vents. It is like my a/c was on but there is not cold air coming out of the vents.It is hot air from outside. If I turn the knob to off it is still blowing air. It turns off when i start the car. Has anyone run into this situation or is this some feature the car has?

Any help would be appreciated
 
#2 ·
It is actually normal. The malibu is built with an afterblow module that comes on after running the car for a bit. It comes on somewhere between 10-15 minutes after I believe. Then it runs for a bit and then shuts off.

It's purpose is to dry off the evaporator core some so mold does not build up on it from the moisture and cause an odor. I think the module is generally set to be on in humid climates, or it can be turned on if a problem occurs. I actually turned mine on because it started to smell some. Since then I haven't had any odors come back.

Now if it comes on and stays on the whole entire time the car is off, then it isn't normal. Also, if you don't want it to do that the dealer can shut it off with the tech II, so that way it doesn't come on at all. Takes me no time at all to do it if I have to.
 
#3 ·
Thanks for the response chevyguy8893, it only comes on for a short time and then shuts off. I dont mind that it comes on cause I live in Southern Louisiana where it is very humid. I just wanted to make sure that this was not a serious problem. You have put my mind at ease.

Thanks Again
 
#4 ·
No problem, it is good that it is on then. I have had cars come in that have horrible odors coming from the vents because of the mold, and it isn't easy to get rid of. From what I have encountered around here, not too many people know that it may be there and can be turned on.
 
#5 ·
Can it be turned on any other way or only at the dealer?

How long after shutting the car off does it turn on?

Will it turn on when the key is in the ACC position, or only when OFF and key is out?

Do the doors need to be locked for it to engage?

Where I live it gets quite humid so I'd like to have this feature turned on. I wanna first see if it's on, then if it's not get it to be so.
 
#7 ·
Michelle -- is this a feature that we can turn on and off ourselves?

Also, how do we know if it is on or off?
 
#8 ·
Alright, so to enable the afterblow module has to be done by the dealer with the tech II scan tool. It has to be enabled through the BCM and setup the HVAC control module through there.

The module will only command the afterblow on as long as there is 12 volts, the outside air temp is at least 70 degrees Fahrenheit, and the A/C compressor operated during the last key cycle. If all the conditions are met the blower motor will come on after 30 minutes of the car sitting with the key off. When it is on the blower will run anywhere between 2 minutes and 30 seconds to 4 minutes. It will only run once after each key cycle.
 
#10 ·
Thanks CG. That good info. I'll have to ask my Service Advisor at the dealer to check it out the next time I go in. It will start getting humid here in the next month or so and I'd like to make sure that's working. Mold in the air vents with mold allergies wouldn't be a fun way to drive. ;)
 
#13 ·
Your part of the country deals with lower humidities than the Deep South so it may not have the feature enabled. If not, and until or if you have the dealership turn it on, you can do something to discourage that smell.

When you use your AC (it's automatically used during Defrost as well) pay attention to when you're getting close to your destination. About a mile or two away (a couple minutes) turn your AC off so it's just air flow. That will help dry the heat exchanger ("cold" exchanger??? ;)) from the condensation that collects on it. That is a large contributor to the smell because it can grow bacteria and other unwanted things. Drying it out slows or prevents the smell.
 
#15 ·
I am not sure what a dealer would charge to do something like this. It really doesn't take much to do unless there is an odor that has to be taken care of too. Anytime a vehicle has come in and I turn the module on is when there is an issue. At the same time there is a chemical that has to be sprayed on the evaporator core to kill off the mildew.

Since it may vary between dealers you may just want to call the dealer and see what they say it would cost.
 
#17 ·
The AC is like a glass of iced tea on a summer day. When you set it down the outside begins to sweat by condensing the humidity in the air - the more humidity the more it will sweat.

Your AC condensation collects in the bottom of the airbox and then drains out under the right side. When the AC is on it will make water and start to drain; when the AC is off the water will gradually stop collecting and the dripping will slow and stop. It's completely normal for the AC to drain while running but not while the engine is off (except as noted).
 
#18 ·
Hi ChevyGuy8893:

I am very appreciative of this thread. I have noticed recently that my Bu sometimes has slightly moldy smell coming from the vents when I turn the car on in the morning. It goes away quickly and then the car is fine, but I can definitely smell it for the first few seconds. Next time I bring the car in, I will ask about the afterblow module.

I hope this isn't a dumb question, but where in the Malibu Owners Manual can I find information about this feature of the car? I flipped through the section on climate control and couldn't find anything that seemed to describe this type of function. I also searched the PDF version of the manual that I downloaded from the Chevrolet Owners Center, and nothing came up. Maybe I am not entering the correct search terms?

Thanks again! :)
 
#19 ·
No questions are dumb questions:), I am always happy to help. As far as I know there isn't any information about it in the owners manual. I am not sure why it isn't in there because it is weird when it comes on and no one knows it exists.

The best thing to do when there is an odor, have the module turned on at the dealer and then take a can of lysol (your preference of scent), and then spray it through the vents on the wiper cowl. Have the vehicle running with the air on, not recirculate, and this will pull the lysol through the system. After you are done spraying turn it over to recirculate and close the car up. Let it run like that for about 10 minutes and it will get rid of the odor. Just be sure not to lock your keys in the car.
 
#21 ·
I am not sure what a dealer would charge to do something like this. It really doesn't take much to do unless there is an odor that has to be taken care of too. Anytime a vehicle has come in and I turn the module on is when there is an issue. At the same time there is a chemical that has to be sprayed on the evaporator core to kill off the mildew.

Since it may vary between dealers you may just want to call the dealer and see what they say it would cost.
Hi Folks!

Just an FYI: I have an appointment next Thursday for my dealer to turn on the afterblow module. The dealer is not going to charge me anything for this service. Personally, I think that's the way it should be. If the feature comes with the car, I shouldn't have to pay an additional fee to use it.

Anyway, others who want to consider getting the module activated may find this information useful when they speak with their dealers.

Have a nice Friday, everyone :)
 
#22 ·
#99-01-39-004C: Air Conditioning Odor (Install Evaporator Core Dryer Kit and Apply Cooling Coil Coating) - (Jun 12, 2009)


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


Models: 1993-2010 GM Passenger Cars and Trucks (Including Saturn)

2010 and Prior HUMMER H2, H3

All Equipped with Air Conditioning




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

This bulletin is being revised to add the 2009 and 2010 model years. Please discard Corporate Bulletin Number 99-01-39-004B (Section 01 -- HVAC).


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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.

Important: 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).

Important: 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.
 
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