Chrysler Repair: 94 Concorde blowing warm air non-stop, oxygen sensor, gas mileage


Question
QUESTION: Hi,
 I got a 94 Concorde around two years ago. It got this problem since then. And no one knows how to fix it including the dealer. The problem is that the AC kept blowing warm air when driving or when the power is just turned on. When this happened, the AC control panel would not work at all, the temperature display LCD black out, the fan seems turn on at highest speed and the air only came out from the vents under windshield. I had tried turning the power off and then turn it back on (did not start the car), which did not stop the blowing. I thought this might be due to overheat of the car, but it is not because this problem came back again and again even while the car was turned on under cold temperature. The dealer ran the computer diagnoses and no error code showed up. Therefore, they did not have a clue about what the problem is. About two months ago, I found a temporary solution for this problem. When it happened, I punched the right side of the AC control panel (the passenger side). Then, it went back to normal. Besides, I do always get the check engine light on. The fault code I got is 12-33-21-55. There is one more issue might be related. The low gas light some time goes on for several seconds then goes back to off while gas is not low. So, I am wondering what really happened to my car. Is it worth to fix this problem? Is it easy for me to fix by myself?


ANSWER: Hi Jacky,
On the last points, there is no relation between the codes and the ATC problem as far as I can see. The 33 says there is something wrong with circuit that powers the clutch that is necessary to run the AC compressor so you might not have A/C for that reason. The 21 says that an oxygen sensor is not working properly which raises the pollution from the tailpipe and reduces the gas mileage, so you might want to address that one by checking the wires and if OK then replace the sensor. As you didn't mention the engine I can't be more specific about the sensor set-up. The flickering low gas warning is fairly normal for an older vehicle as the internal level sensor may develop intermittent open areas on the resistive slider that operates it.
On the blower problem, it sounds to me as if the power to the ATC control unit is absent. The main current source is fuse #6 which is under the dash on the driver's side. So take a look at that fuse to see if it is blown or has a crack in its wire. If that is OK then the wire from the fuse to the plug (white wire on pin 5 of the plug) at the back of the control should be checked, and finally while the control is removed I would check to see if the pin for the socket where it connects to the circuit board of the control unit might be unsoldered which could be corrected by simply reheating the joint with a soldering pencil. So if you want to do those checks that would be a way to solve it yourself. Let me know any specifics you need to do them.
Roland
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---------- FOLLOW-UP ----------

QUESTION: First, the engine is 3.3L. I check the fuse #6, it's OK. And, found the plug as well as the white wire. The wire seems to be okay too. But, I don't not how to check a other end of this wire. Where does the wire goes? Do I need to take the dashboard out? I don't have the knowledge of doing that. And, I have no clue of how to check the Oxygen sensor either. So, can you help me a little bit more?
Thanks,
Jacky

Answer
Hi Jackie,
To check the wire from the fuse #6 to the plug on the back of the ATC unit, you need either a voltmeter or a 12volt neon glow lamp toe measure for the presence of voltage then the ignition switch is in the "run" position. Whichever device you use, just verify by touching one of the probes to the 5 pin of the plug and the other end to pin 2 of the same plug which should have a black wire. If you get a reading or a glow from the glow light then you know that the power is arriving via the plug. So then you need to take apart the ATC control unit and look at the socket for the plug and take a soldering pencil and reheat the joint for the 5 pin and the 2 pin as that may be the reason there is no lighting of the dial and no control of the blower or temperature. If that doesn't work, then a part inside the control is blown and you would need to get another one at a junk yard (the least costly solution).
On the oxgen sensors there is one on each exhaust manifold and you would need to measure the voltage between the the black/dark green wire and the engine block on the one on the left side exhaust manifold and between the tan/white wire on the one on the right side exhaust manifold. They face the engine block. To see the one on the right you have to remove the air cleaner resonator and hose. The wires I speak of are on the side of the disconnect plug for each sensor that is going to the wiring harness. You need to insert a straight pin thru the insulation to gain access to the conductor inside, then attach the probe to the pin.
You will find the sensor on the sides of the manifold near the rear of the engines and they have 4 wires each attached to them. The reading of a good sensor will be around 0.5 volt with the engine running. That is how to tell which one is good, or perhaps both are bad, the code just tells you something is wrong. You will need to measure to decide. The look like spark plugs.
Roland