Some cars have a vent switch which allows outside air inside. Perhaps the switch is broken, and it is not turning the blower off as it should. If you open the hood, you can usually see the blower motor. You could unplug that and see if it still blows.
if the fan continues to run after shutting thermostat completely off, possibilities include bad fan relay on thermostat, trouble shooting further, if control wiring is disconnected from thermostat( check for shorts) and fan continues to run, you have the contacts on the fan relay stuck together, and need a new relay.
Air conditioners have a number of electrical components. A stuck relay switch allows an electrical circuit to remain closed, constantly providing power to the air conditioner. The compressor contactor can fuse in a closed position, allowing the condenser unit to keep on running with constant power.
When climate control isn't on recirculate the exterior vents are open, taking in air from outside. Your motor produces heat, your radiator fan blows that heat off the radiator, and it ends up blowing into the cabin because the exterior vents are located in the engine bay.
Clogged Air Filter: A dirty or clogged air filter can restrict airflow, causing the system to overheat and shut down. After it cools off, it may start blowing air again. Regularly changing or cleaning the filter can help prevent this.
You could have a dirty air filter, clogged condenser coils, frozen evaporator coils, a broken relay switch, or a bad thermostat, amongst other common air conditioner issues.
This process, called after-run cooling, is a built-in safety feature in most cars, designed to prevent the engine from overheating when it's no longer running. It's usually nothing to worry about, but if the fan runs excessively long, there might be an underlying issue.
The compressor is failing and can't generate enough pressure to reach the cut out pressure. The high and or low pressure switches have failed and are sending the incorrect info to the cycling relay. The compressor clutch relay is sticking on. There is a short causing the clutch relay to remain on.
In AC systems, the air conditioner reset button is on the outside unit's lower edge, typically close to the ground. Some models have the reset button located behind the service panel, which may require tools to remove. Reset buttons are usually red or yellow with a clear “reset” label.
This could happen for a wide variety of reasons, such as a faulty wire, broken switch, or blown fuse. Another common reason is your compressor not turning on because it doesn't have enough refrigerant. Most compressors won't turn on if they go below a certain refrigerant level.
This isn't necessarily bad for your fan, but it is usually a sign of a bigger problem. Common causes for fans not turning off when they should include faulty thermostats, bad wiring, and stuck relays. These problems are not easy DIY repairs and should be left to an HVAC professional.
On the other hand, you should avoid doing so when the car engine is off. That s because it will consume almost the entire battery power within a short span. Thus, you may have to jumpstart. Even if you run the air conditioning with the engine not on, there would be no cool air.
Under normal conditions, an air conditioner running in a properly sized system should cycle for about 15-20 minutes before shutting off. This length of time allows it to cool the air effectively, reach the desired temperature, and then turn off to save energy.
A refrigerant leak can disrupt the cooling process and cause the AC to blow warm air. Even when the system is turned off, a leak can lead to the circulation of ambient air through the ducts. If you suspect a refrigerant leak, it's crucial to contact a professional AC technician to inspect and repair the issue promptly.
Essentially, there are two components that can stop functioning, triggering a failsafe mode that causes the fan to run continuously. The first is the fan relay, which due to age or corrosion will stop switching the fan on and off.
A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.
Power down your AC: Turn off your AC unit and unplug it from the power source. This will ensure that you stay safe while working on the unit. Locate the reset button: Most air conditioning units have a reset button located near the outside unit. It is usually a small button located inside a small hole.
You shouldn't notice air coming from your vents when the AC is off. If you do, there might be an issue with your thermostat or AC settings. Alternatively, you might have a faulty contactor or bad wiring. Contact an HVAC pro to identify and solve the problem.
The symptom you are describing here, can be one of two different things. This can either be a faulty Blower Motor Resistor (or a circuit to it) or the Control Head itself (the unit in the dash with the knobs).
If only the fan is running when the AC isn't, there may be a faulty relay switch stopping the settings you enter on the thermostat from being communicated to the fan. It's also possible there is another wiring issue or short circuit preventing the on and off commands from going to your fan.
Malfunctions affecting different system components can prevent the conditioner unit from shutting down as expected, such as a clogged air filter, a frozen evaporator coil, a faulty electrical relay switch, a dirty condenser coil, a constantly blowing fan, a bad thermostat, low refrigerant, and other HVAC system repair ...
If your air conditioner keeps running when it's turned off this could be a sign of shorted thermostat wiring. A continuously running air conditioner could also be triggered based on the settings selected for the unit.
Air can enter the coolant system in other ways besides just from a leak. Coolant fluid changes are required as part of ongoing maintenance for all vehicles, and when these procedures aren't properly executed they can cause air to leak into the coolant system, creating odd noises to occur once the car is turned off.
Engine blow-by can occur within both diesel and gas engines. Piston ring wear or other component issues can lead to combustion gases leaking into the crankcase, often creating visible excess gas release from your generator.