I've just spent a couple of hours reading numerous threads with interesting problems with air conditioners. I could not find one that aligns with the symptoms my wife experienced today.


With the A/C on the air coming out of the vents on the driver's side was warm, but reaching over she could feel that the air coming out of the passenger side vents was cold.


Since the car has dual zone controls, I concluded that there must be sensors that detect the cabin temperature on each side, and signals the delivery of cool air appropriately, and that the driver side sensor may be bad. So I searched the service manual, and it seems there is only one "room temperature sensor," although there are two temperature control switches.


So I have 2 questions.


Important question: What might cause one side to work and the other not to, and how can I diagnose further?


Curiosity question: With only one room temperature sensor, how can the neural network control figure out the outlet temperatures to achieve the settings of the temperature control switch?


Thanks to anyone who can help.

 

The neural network has several sensors to determine the AC output. Besides the cabin temp sensor, it will use the ambient temp sensor, evaporator temp sensor and believe it or not, two solar sensors to determine which side of the car the sun is shining on to determine how to split up the temp in the outlets. In your case, it could be the blend door, the solar sensor or the cabin temp sensor that could be causing the issue. It will take some time with a scanner and DVOM to find out the problem.

If you want to tackle this yourself, let me know and I might be able to help some but your best bet would be to get a manual or invest in Mitchel or AllData online manuals. They will help you a lot in trouble shooting the AC system

 

Hi David,


Thanks so much for your guidance and offer to assist with this problem.


I do have the Factory Service Manual, and know how to use a DVOM. I also have an Actron CP9180 scan tool, but I don't think that can read the DTC codes related to the cooling system. I could not find a symptom like mine in the trouble shooting table in the FSM.


I think I understand how to test the cabin temperature sensor and the ambient temperature sensor. It's just a matter of checking the resistance across the two leads and comparing it to the tables in the FSM. It looks like the Intelligent Tester is needed to test the solar sensors. I also cannot find a reference anywhere to the blend door you mentioned.

While testing the resistance across the ambient temperature sensor will determine whether it is bad or not, isn't it safe to assume it's okay if the temperature reading on the dash display is correct?

I checked prices on the sensors online, and the ambient temp sensor is less than $12 and the air temp sensor is less than $20. Is it cost effective just to replace them before taking the dash apart to get to the solar sensor?

In what order would you test the components in diagnosing this problem? You mentioned the blend door, the solar sensor or the cabin temp sensor as possible causes. Would one be more likely to be bad than the others? Is one easier to access and therefore should be tested first?


Thanks again for any advice you might provide. (Even if you tell me I should take it to the dealer to diagnose, I'd respect that advice.)


Best Regards,


Rob

 

More information: Two new problems cropped up:

Sometimes when we push the door lock switch on the outside of the driver side door, all doors will lock and unlock correctly except the driver's door. When that happens, the beep does not sound.

My first thought was, "oh good," if the same cause is at the root of both problems, it might be the battery. After all, it is a 2007 with 154,000 miles on the original battery! The voltage across the terminals is 12.84 with the engine off, and 14.41 with the engine on, so the easy diagnosis doesn't hold.

The second piece of new information is that now cold air does not come out on either side (before it was just the drivers side).

Does that tell me that the A/C problem is probably either the amplifier, or the ECU, and the lock problem is either the door switch or the ECU?

 

First things first, replace the battery. It will be a lot simpler in your driveway tyhan sitting on the side of the road somewhere.....

Next, your door lock issue is more than likely the solenoid or the plug/wiring to the solenoid but that can also be caused by a low voltage condition. That is why the battery comes first....

The air conditioner could be a LOT of issues. Low fluid level, amplifier, sensors or a dozen other things. By the way, I still call them a blend door but the official name is "Air Mix Control Damper" It might be cheaper in the long run to have the AC system looked at by someone with a bi-directional scanner/lab scope that can test and see the raw input from the sensors.

The last thing I would suspect is the BCM as they are usually pretty bulletproof.

 

Thanks, David. Why are you suggesting the battery should be replaced? Just because of age? I think those voltages are within proper range. The FSM says the battery voltage should be between 11-14V.

I had the dealer check the A/C yesterday, and indicated it is essentially empty of Freon. They filled it with gas with a stain and want me to drive it for 2 weeks to attempt to find the leak.

They were not able to duplicate the door lock problem and suggest the problem is the FOB battery. I doubt that because the problem was with both my FOB and my wife's FOB, but that's cheap enough and easy enough to test.

Now for the bigger favor/question for you. I occasionally have problems reconciling the part reference in the factory service manual with the parts on the microfiche because of naming differences. Neither source discusses a solenoid, but obviously there is one that triggers the unlock/lock. This link goes to a front door microfiche page: http://www.trademotion.com/parts/200...agramCallOut=7. I had assumed I might need part #7 (8999106010). Are you referring to the Lock Assembly, part #11 (690400C050)?

 

Rob,

Any car that is 8 years old with 154,000 miles is past the life expectancy of the original battery. The resting voltage should be roughly 13.2 volts on your battery and this is one of those "ounce of prevention" items that should be done. A low voltage condition can cause a LOT of problems in modern cars and leave you sitting in a parking lot somewhere wishing you had changed it....

Yes, the lock assembly contains the solenoid that activates the locking mechanism. Check the wiring connection for corrosion or loose connection/wiring before replacing the lock as they are not cheap at all.... The wiring can be checked to make sure a signal is sent to the lock when you lock/unlock the door. You know the car is receiving the signal as the other doors work, you just need to find out where the drivers door is having a problem.

 

Thanks again! I will replace the battery, and test the door wiring connections before ordering the locking mechanism. I appreciate you help.

Indeed, you've helped me many times before through your answers to many people.

 

Correct me if I'm wrong, but isn't AC comp running off 12V battery?
OP, when you replace 12V battery, make sure to have a jumped back up one connected to terminals, just for the hey of it. I saw one user that landed with over 4500 in repair costs after "simple" battery swap. P jumped mine. Still all jistorical mpg data were lost. But that's a small price for peace of mind.

 

Hate to tell you but the AC compressor runs off of the high voltage circuit (take a look at the orange cable going to it) but the control circuits do use the 12 volt circuit.....