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Old 08-17-2012, 10:45 AM   #6
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Join Date: Mar 2011
Location: Denver
Posts: 2,930
My Ride: 325Ci
Originally Posted by Dre325 View Post
Thanks for the response. I checked the OBD temps today on my commute home from work. I checked the local temp on my phone first and it was 89 degrees F outside. On the hidden OBD 7.1 (ambient temp), I got a reading of 275 with the car off. This varied up to 420 on my 30 minute drive home. I am assuming this is supposed to be in degrees C?? Can somebody confirm that I definitely have a bad ambient temp sensor in the driver's side wheel well?? Sure looks like it, unless I am interpreting the readings wrong. Hopefully this is what is causing my AC to not work.

On the 7.0 coolant temp readings, I had a reading of 33C when first starting my car (or 91F which seems right as it was about 90 outside). It climbed to about 88C (190F) after 10 minutes sitting in stop and go traffic. It then dropped down to 81C (178F) when I finally got up to about 50mph on the freeway. Seems like I need to replace the thermostat, correct?
I dont think there is anything for the P0128 to do with AC. Erase the code and see if it returns. For AC, I cant give you much information but I am pretty sure that its not caused by the thermostat. You should get the AC checked by a qualified tech, our AC systems are known not to be messed with, with little knowledge.

Did you check the temp gauge after driving for sometime. Does it stay at the middle or slightly to the left?
If slightly left of the 12 o'clock position, classical case of open thermostat.
Change the thermostat first and see if it helps the AC issue too, I doubt it will but never hurts to try.

The only issue you will face with open thermostat is, the engine will never reach the optimal temperature, hence more fuel will be burnt. Result: a little decrement in MPG.
trj is offline   Reply With Quote