What is wrong with my climate control?

ANSWER : A temp sensor malfunction could be causing your problem. If the controller is getting bad information, it’s going to operate the doors according to that information. So a sensor replacement is indicated. However, these systems can also have problems with the stepper motors themselves that drive the flaps. All the little plastic gears can get jammed up. In most cases, the self diagnostics will catch that and give you a code, but not always. If you have the right scan tool, you should be able to activate the motors and watch them work. Working on the climate control can be difficult and time consuming, if you want to have the job taken care of for you, contact YourMechanic and they’ll send a technician to your home or office to diagnose your climate control issues and advise you as to what to do about it.

ANSWER : A/C systems that used fixed displacement compressors will cycle on and off (the compressor that is) depending on cooling demand. If you have a variable displacement compressor in your vehicle, though, the compressor may hardly ever cycle simply because the compressor is capable of load following. In fixed displacement systems, without automatic climate control, the rate of cycling is usually determined by pressures within the system. An example of this type of system is what’s known as a CCOT (cycling clutch orifice tube) system. The compressor clutch will cycle on and off depending on cooling demand, usually at around 21-23 psi on the suction side, but of course there is variance from car model to car model. On newer car, the vehicle’s PCM is involved in the control strategy, too, as the PCM can command the compressor off during periods of high engine demand, such as rapid acceleration. Insofar as climate control heating and HVAC systems, those are electronically controlled and, in the main, merely "automate" all the mechanical controls that formerly were used to control the position of blend doors and the heater control valve. Control strategies are electronics-based. If you need a diagnostic of a vehicle HVAC problem, performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request HVAC inspection/testing and the responding certified mechanic will address your issue(s). If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

ANSWER : If your Fusion has the touchscreen navigation system installed, then it’s tied into your Automatic Climate Control system as well. You’ll find that some of the physical controls on the HVAC system are duplicated on the touchscreen (that way, if the touchscreen doesn’t work you can still control all aspects of the system). What can you control from the touchscreen? Here’s a quick rundown:

Temperature Conversion: Not happy with the Fahrenheit readout? Use this to change it to Celsius.
Temperature: You have two temperature controls, one on the left of the screen and one on the right. Use the left one to control the driver side temperature (and the passenger side if dual zone isn’t active) and the right one to control the passenger side temp.
Vent Controls: You have four vent control options on the touchscreen, including:

Defrost and lower vents
Upper vents
Upper and lower vents
Lower vents only

The Active Vent setting displays at the top of the screen:

Fan Speed: Use this to adjust the fan/blower speed.
Dual: Press this to turn on or off dual zone climate control
Max A/C: Turns on maximum air conditioning.

ANSWER : You’re getting into an area that is kind of a dark art when you’re getting these kinds of codes. While I don’t know any of the symptoms that the car is exhibiting, I can tell you that failure in one of the control units can lead to codes showing up in the others and the ABS, ESP is a likely culprit since it interprets the wheel speed signals and sends the information to the other modules. You’re right that the module has to be coded, and I don’t think that Snap On has the software for that so the only place to go is the Star Diagnostic. (The consumer version of the Mercedes SDS ) You can Contact YourMechanic and see if anyone in your area has the appropriate equipment for this. Otherwise, this may be a case that would best be consigned to the Mercedes Dealer.

ANSWER : Hi there. The trouble code you indicated is similar in many ways to the P0963 OBD-II code. This article should give you a lot of valuable data that will explain the source of this code, possible causes and repairs. In general, this code is related to a communication error with the transmission pressure control solenoid. Most of the time, the code is triggered due to the solenoid being dirty, or the connections are loose. When this happens, the OBD-II trouble code essentially activates a fail safe mode, so that the car will not continue to damage the transmission or other components.

ANSWER : Hello, thanks for writing in. I’d be happy to help.

From what you describe it appears that your vehicle is experiencing some sort of electrical issue. It may be possible that the some sort of wiring problem has occurred, or that the components you replaced are defective. I would carefully inspect the vehicle for any wiring issues, though from what you describe, the unit operating in reverse, it is more likely that the component is defective. It is not uncommon for aftermarket components to be defective out of the box, so if you suspect the component may be defective, I would replace it. A wiring diagram can be sourced from either the dealership, or out of a quality service manual.

If you would like help inspecting the electrical components, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make any repairs as needed.

ANSWER : Hello. This can be caused by a number of different issues. Most of the time this is caused by a bad brake switch. If the switch is shorting out, then it will cause the computer to think that the brakes are being applied, which turns off the cruise control. If the switch is fine, then it may have a bad speed sensor or the cruise control switch itself is bad.

One of the easiest tests I do is simply have someone drive behind me and see if the brake lights are coming on without touching the pedal. If it is, then you should replace the switch. If not, then further testing of the circuit has to be done. If you need to have this done, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose your cruise control problem.

ANSWER : Hello Dennis, thank you for writing in. The automatic climate control uses a cabin temperature sensor, blend doors, and engine temperature sensors to regulate the air coming into the cabin. There may be an issue with any of these components, or the communication between them. There are several other complaints about the system, and the best way to go about it is to make sure the sensors are calibrated correctly. You should also if needed test to make sure the blend doors are activating and working to keep the temperatures properly regulated. Considering your symptoms, you may want to focus on the cabin temperature sensors first. For more help resolving the issue, contact our service department to schedule an appointment.