Today’s automatic climate control techniques make it possible for hands-free temperature regulator, irrespective of whether hot or cold. Once you set a temperature on your car’s automatic climate control system, it need to maintain that temperature irrespective of what’s going on outdoors.


Manual air conditioning systems are just what the name implies: they call for he A/C temperature settings to become adjusted manually. Manual A/C systems have an on-off switch, a temperature manage knob or slide switch along with a knob or switch for adjusting fan speed.

Using a manual A/C system, you turn about the A/C when you want great air and select a temperature setting and blower speed. If the air gets also cold, you turn down the blower speed or modify the position of the temperature setting. When the air is not cold enough, you crank it all the way up.

The temperature slide switch on most manual methods is linked with cables or vacuum hoses to the airflow manage doors inside the HVAC (heating ventilation air conditioning) unit beneath the instrument panel. Transforming the temperature setting opens or closes the doors to boost or decrease airflow through the A/C evaporator. It’s a fairly simple, trouble-free manage system that won’t require a lot of challenging electronics.

Automatic temperature control techniques, by comparison, may be incredibly complex (and troublesome). These style of programs management the two heating and cooling having a single temperature setting. The system then monitors the temperature within your car and instantly chooses heating, cooling or a blend, and also blower speeds to maintain the desired temperature you might have selected.

“Dual Zone” automatic temperature management methods that happen to be presented in lots of newer motor vehicles permit the occupant of each and every front seat to decide on their own comfort setting. One side can blow awesome air along with the other side can blow warm air.


Sustaining a relatively consistent temperature setting will not be as uncomplicated since it sounds since the temperature within and outside the car is continuously modifying. The ambient (outdoors) temperature has an effect on just how much heating or cooling is necessary to heat or amazing the incoming air to the preferred temperature. Sun load can also adjust the interior temperature and cooling specifications.

Because the air temperature inside your car slowly adjustments, the automatic climate control system must compensate by altering the blower speed and temperature settings. It truly is a continuous balancing act that requires many inputs and controls.


To regulate the temperature within your car, the automatic climate control system utilizes an ambient air temperature sensor outdoors the passenger compartment, one or even more in-vehicle air temperature sensors (which may involve an “infrared” sensor that measures the actual body temperature of you and/or your passengers), a “sunload” sensor to compensate for sunlight getting into the motor vehicle via the glass, one or more electronic control modules, and vacuum or electronic controls for the various HVAC airflow management doors.

Nearly all of the newer automatic climate control methods use small electric motors (actuators) to operate the airflow doors in the HVAC unit. There are actually 5-wire, 3-wire and 2-wire motors, all of which operate in a different way and have to be replaced with all the exact same sort of motor. The 5-wire motors possess a feedback circuit to help keep the handle module informed about their place. The 3-wire “smart” motors often have their very own microchip to regulate and self-calibrate their place. The 2-wire motors are very simple reversible 12-volt motors that push the airflow doors one way or the other. The controller keeps tabs on their position by running the motors total open and total closed, then counting the revolutions on the motor armature to figure their precise position. Like we mentioned, they’re complex, sophisticated systems.

Some motor vehicles, this kind of as late model Chrysler minivans, have a “triple-zone” automatic climate control system. This system has separate controls for your driver, front passenger and rear passengers, and uses infrared sensors front and rear to monitor cabin temperature. What’s more, it makes use of a “smart” 2-wire electric motor to manage all of the blend air doors in the HVAC system. The motor not only operates the doors but keeps the management unit informed about its exact position. The system has 22 different management modules that communicate back and forth in excess of a common bus network of multiplex wiring.

Another instance of how complex these systems can be is Mercedes C320 dual-zone automatic climate control system. Unlike most other A/C methods that cycle the compressor clutch on and off to regulate the refrigeration circuit, this system has no clutch around the compressor. The belt-driven variable displacement compressor runs all of the time and is managed by a pulse width modulated signal from your A/C control module (extra and even more new cars are switching to this type of A/C system). Cooling is controlled by varying the compressor’s output from 2 to 100 percent according to the cooling load about the system. Mercedes also utilizes a “smog sensor” to near off the outdoors air inlet if it sniffs hydrocarbons or other poor odors. 10 electrical motors are utilised to manage the several mix doors inside the HVAC system, and a sunload sensor about the dash modifies A/C/ output to compensate for sun load. Even the engine cooling fan is also partially managed by the climate control system, and 15 different interior handle modules are made use of to regulate cooling inside of the passenger compartment.


Troubleshooting an automatic climate control techniques is generally past the talents of a do-it-yourselfer since it normally demands specialized training and equipment. If an A/C cooling problem is not thanks to a fault within the refrigeration circuit (terrible compressor, plugged orifice tube, reduced refrigerant, leaky evaporator, and so forth.), you could probably blame the automatic temperature control system. To learn why, difficult, normally demands the usage of a scan instrument that could access and read HVAC codes (which ordinary engine-only scan tools can not), and a digital voltmeter to check circuits and sensors.

Most late model automatic temperature control methods have self-diagnostic abilities and will crank out fault codes that indicate the nature on the challenge. But in most cases, a technician nonetheless must look at many elements by measuring voltages, resistance, searching for opens or shorts in the wiring, etc. just before he replaces an parts (in theory, anyway).

Accurate diagnosis is extremely significant on these methods simply because quite a few replacement parts might be Extremely high priced. Parts like management modules can expense hundreds or even a huge number of dollars to substitute, dependent within the car application. Other parts such as sensors, switches, relays, resistors, vacuum valves, vacuum motors, electrical motors and blower motors won’t break the bank when you have to change one, but the labor to install a few of these parts (when you do not do it your self) can take hrs.

Tearing apart your dash plus the HVAC system could be a pretty time-consuming and daunting activity. So unless you will be a really skilled do-it-yourselfer, this really is one career you must let a professional do for you.


No cooling (air blowing out of ducts is warm when it really should be interesting).

This could be a fault from the refrigeration circuit (negative compressor, plugged orifice valve, blown fuse or lousy relay, low refrigerant or no refrigerant in system), or it could be a lousy Mix AIR door handle motor in the HVAC unit that is just not routing the air as a result of the A/C evaporator.

Temperature doesn’t match the desired setting (also warm or also cold).

The system might possess a negative interior temperature sensor, or perhaps a bad Blend AIR door manage motor inside the HVAC unit.

No air blows out of ducts when A/C or warmth is turned on.

Possible causes here incorporate a bad blower fan relay or fan motor.

Air fails to blow out of sought after ducts (dash outlets, or lower outlets, or defroster outlets).

The issue here is likely a bad AIR Management door motor that is not shifting place to route the air to the wanted outlets.

Nothing happens once you turn the automatic climate control system on.

Check out the main system to see if it has blown (refer to your owner’s manual for your fuse location). If blown, substitute the fuse with one that has exactly the same amp rating as being the original. When the new fuse blows, there is a short or overload in the wiring that will have to be diagnosed and repaired.

When the fuse is okay, the control module might have died. The way in which to confirm this would be to hook up a scan tool to see in case the scan instrument can communicate with the management module. No communication would indicate a dead module or maybe a wiring fault.

When the battery was recently disconnected or replaced, some automatic climate control programs will not operate until they are reset with a scan instrument. The relearn procedure teaches the management module the positions from the a variety of air flow management doors so it can handle air flow and temperature.