Expert: Roland Finston - 6/17/2011

Question
Hi Roland, you've helped me in the past, Hope you can do it again. I recently purchased a used 2003 PT Cruiser w/auto transmission. The 2nd day i drove it, when stopping at an intersection my 'check engine' light came on (the one that looks like a valve icon). You helped me w/this same light on my 2002 manual trans. pt cruiser that turned out to be the power steering pressure sensor switch..which i fixed as per your instructions, and got that car to pass inspection, only the next day a hit and run driver totaled that car, and this 2003 pt cruiser i'm asking about was what i purchased with the insurance money. Needless to say i was disappointed to have that very same light come on the 2nd day of ownership!  ANYWAY, a clerk at Auto Zone put some electronic device on my car and told me the dashboard icon was lit due to a bad Ambient Air temperature sensor.  Additionally, it appears the a/c on this vehicle really doesn't work well at all, only blowing cool air occasionally in the early, cool morning hours, but in the heat of the day just blows hot.  Might the dashboard indicator re: the AAT sensor and the lack of working a/c be related?  I fear i may have bought myself a bad egg and the purchase, as with most 'used cars' was 'as is'.
Any advice, help you can give would be appreciated!

Answer
Hi Denise,
The sensor doesn't appear to be involved with the AC system, but repair that first and then if the AC is unchanged I would believe that you may simply need to add some refrigerant to its system to get it to run reliably.
The sensor is possibly located behind the grill and in front of the radiator/ac condenser assembly, mounted on a bracket. The two wires run between it and the overhead console and pass through three disconnect plug/socket assemblies so you might want to check the wire continuity first before buying the sensor.
The black/light blue wire should be connected to pin 11 at the console while the violet/light green wire should be attached to pin 5. The sensor may actually be found in the left front wheel well area, near the left fog lamp so look for a small device with the two wires I described connected to it. If you don't find it there, then look between the grille and the radiator assembly. The manual mentions both places so I can't be certain.
To remove the overhead console to check the wire continuities: grasp the front of the console and pull downward to disconnect the front retaining clips, then slide it forward to disconnect the rear tabs from the headliner. Then you can pull the plug and check the wire continuity from the sensor to the plug. Of course if the sensor is not too expensive you could try replacing it first and avoid the wire issue unless a new sensor doesn't correct the problem with the light being on.
Let me know if the wires are the problem and I can tell you where the disconnects are located so you can check them and figure out where the wire problem specifically is located.
Don't be upset about these sort of issues, they are common and easily fixed. The AC refrigerant can be added yourself with an adapter and a can of refrigerant, or an AC shop can check it out.
Roland
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Thank you