When hot outside, bad odor from vent when on

When the weather outside got hot, I had my vent blowing (not the air conditioner) and there was a very bad smell. So bad that I got nauseated. I took it to the dealership 4 times for this same odor problem from the vent and no one knows what the smell is, nor how to get rid of it. They ran it through an Ozone cleaning system and deodorized the A/C unit 3 times (even though I don’t think it’s the A/C). There is also a loud buzzing sound that’s coming from the driver’s side window. This happens when the wind blows on it. There is also a clicking sound that I think is coming from the pass
Experienced mechanics share their insights in answering this question :
It is possible that your evaporator may have fungus growing on and it’s so thick that the cleaners you are running are of no use. In extreme cases, the evaporator will actually need to be replaced in order to get rid of the foul smells coming from its growth.

This issue all starts with an improperly functioning evaporator drain tube. If this drain tube gets clogged, it will allow moisture to remain inside the dash near the evaporator. Due to the fact that this is a dark, cold, damp place, the likelihood of having mold growth is high.

It is also possible that you may have a small rodent that died inside your dash somewhere. To determine this for sure, a telescoping inspection camera may be required. This camera will be inserted into the dash vents and is able to bend around corners to see things that you could not see with your eyes alone. If dead animals are found inside the dash, it may be necessary to remove the whole dash in order to remove them. If this is the case, ensure this job gets performed by a qualified professional to ensure everything goes back together properly.

If you decide that you need help with this, feel free to contact a certified mechanic who can pinpoint the smell you are experiencing and make the necessary fixes to get the odor out.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Smells in your ductwork can be caused by a variety of sources such as mold and mildew, animals in your home or ducts, duct leaks, plumbing leaks and issues, building materials, or mechanical issues, such as a leaky (and unsafe) heat exchanger or a bad blower motor that is overheating.
Dusty and Dirty

Air filters collect dust mites, dirt, and pollutants, the buildup of which can cause an unpleasant smell from your vents when you use the AC or the heater. This putrid smell can be avoided by replacing air filters every 10,000 to 15,000 miles as recommended by the vehicle manufacturer.

When too much dirt and debris build up on the filter, airflow will be more restricted. This can put a huge strain on many components of your AC system, resulting in this burning smell. We recommend changing your air filter every month or so in the future so you don`t experience this concerning smell again.
Baking soda is an ideal fix for odor coming from air conditioning vents, as it naturally absorbs all sorts of smells. If the AC smells bad and the odors are coming from inside the ducts, you may have to put the baking soda inside the ductwork for maximum effectiveness.
Rotten Egg Smell Coming from Car Vents

A rotten egg smell in your car often indicates a malfunctioning part in the fuel system. If the catalytic converter, fuel filters, or fuel pressure sensors are worn out or damaged, a sulfur gas can leak out and make its way into your car`s cabin.

One of the common causes of a musty smell in the home is a clogged condensate drain due to evaporation and condensation of the evaporator coils. Water droplets go into the condensate pan during the condensation process then flow through the drain line. It means the dirt in the condensate pan flows with the water.
If you smell sewage when you turn on your A/C unit, your sewer system may have backed up into your house or near your unit, and the smell may come from a ruptured pipe. Contact an air conditioning company right away if you notice a sewage smell or detect methane in your home. Do not let this problem linger!
Generally, it`s completely normal that a heater has a burning smell when first turned on, and you don`t need to worry! In most cases, this odor dissipates in an hour or so. As long as the smell of burning doesn`t continue for more than a day, this odor is just a normal occurrence.
Plastic – If your heater smells like burning plastic, the odor will quickly become intolerable. This smell likely means that a foreign object, such as a toy or a humidifier nozzle, has become lodged in the furnace and has been slowly baking away.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

When hot outside, bad odor from vent when on
ANSWER : It is possible that your evaporator may have fungus growing on and it’s so thick that the cleaners you are running are of no use. In extreme cases, the evaporator will actually need to be replaced in order to get rid of the foul smells coming from its growth.

This issue all starts with an improperly functioning evaporator drain tube. If this drain tube gets clogged, it will allow moisture to remain inside the dash near the evaporator. Due to the fact that this is a dark, cold, damp place, the likelihood of having mold growth is high.

It is also possible that you may have a small rodent that died inside your dash somewhere. To determine this for sure, a telescoping inspection camera may be required. This camera will be inserted into the dash vents and is able to bend around corners to see things that you could not see with your eyes alone. If dead animals are found inside the dash, it may be necessary to remove the whole dash in order to remove them. If this is the case, ensure this job gets performed by a qualified professional to ensure everything goes back together properly.

If you decide that you need help with this, feel free to contact a certified mechanic who can pinpoint the smell you are experiencing and make the necessary fixes to get the odor out.

I have a bad oxygen sensor, bad power steering sensor, and a bad cam shaft sensor? Should I replace any of them?
ANSWER : When you say you have three bad sensors I can only assume you have had them tested and the end result is three bad sensors. If they tested bad then they should be replaced. The power steering sensor senses the load of the steering on the engine so it can raise the idle during parking maneuvers. The O2 sensor is used for fuel control and it may effect engine power and fuel mileage. The camshaft sensor cay cause no starts, engine running problems and all three will turn on the check engine light.

Ac compressor. Blowing hot air through front vents and cold air through rear vents.
ANSWER : It sounds to me like you have a blend door actuator problem. The blend door actuator is responsible for controlling the blend door. The blend door is responsible for blocking off air to the heater core when your air conditioning is on. I would recommend having your blend door actuator tested using the manufacturer’s recommended procedure. Once this has been done, a qualified mechanic will be able to inform you of whether the actuator will require replacement in order to resolve this issue. If you need help with this repair, YourMechanic offers a repair and diagnosis service preformed by a certified mechanic that will commute to your location to look inspect your heater and AC problem.

Heat blows hot from dash vents but cold from floor/feet vents?
ANSWER : Hi there. This issue is commonly caused by a malfunction with the vent selection switch. In some cases, a fuse or electrical relay becomes damaged which essentially blocks the heater vents from opening and closing correctly. However, it could also be caused by a mechanical component failure in the vent system itself. To diagnose this problem correctly, a professional mechanic should complete a heater is not working properly inspection at your location.

Heater won’t work from center vents
ANSWER : Hello and thank you for contacting YourMechanic. The issue is the blend doors are not adjusting correctly when you adjust the thermostatic switch. Check the wiring in the dash for any loose contacts to the blend doors. Also check the blend doors for any debris trapped in them causing them to stick on the tracks. If you need further assistance troubleshooting your vehicle, then seek out a technician, such as one from YourMechanic, that can assist you with the heater.

While driving defroster set to hot blows hot air as it should, while idling it is blowing cold air.
ANSWER : First, the coolant level should be checked to make sure the radiator is full. While the overflow tank may be full, the radiator cap must be taken off to check the level inside the radiator. If you find the level is very low, you have a coolant leak that must be fixed. If coolant levels are normal, an engine thermostat or heater control problem may be what you’re experiencing. Consider hiring an experienced technician like one from YourMechanic who can come out and take a closer look at your lack of heat concern to offer a more personal diagnosis.

I recently changed out a bad coil pack that had been bad for a month. Literally today it got changed and shuts down while driving
ANSWER : Hello. The bad coil wouldn’t have caused the crank sensor to fail. Crankshaft sensors are the most common failure on this engine so it should just be a coincidence. I would use a scan tool just to make sure that there is no rpm reading before replacing it though, as there are some other problems that can occur, but are not as likely. If you need help with this, consider having a technician from YourMechanic come to your home or office to diagnose this problem with a scan tool and replace the crankshaft sensor if necessary.

Hey i have a 2000 focus and the heat blows hot but it only stays hot for about 1 minute then it goes cold. I have to wait 5 minute
ANSWER : Hi There,
If your heat blows warm and then cold in addition to the engine overheating, this may very well be a thermostat issue. This may also be an issue of air being trapped in the radiator or heater core. This causes this type of cycling effect with hot and then cold air being blown into the cab of the vehicle. I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.