2005 TL - Climate Control - Self Test?

Having a problem with my 2005 TL. Climate control set to "Auto" and a given temp, say, 70F, will only blow cool air even on a cold day well
below the setting, unless, after the engine warms up, I reset the temp well over 80F and then it will suddenly supply heat and, when the control is reset to 70F, it will then maintain it or any other temp change I make the rest of the trip without a problem.
1. Anyone got any idea of what might cause this?
2. Does the 2005 Climate Control have a self test fucntion? If it does, what are the commands to trigger the test?
TIA, Paul
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snipped-for-privacy@verizon.net wrote:

Wild guess, hook up OBD reader and see what comes up. Or another wild guess sounds like temp. sensor is erratic or poor electrical connection for the sensor. I had similar problem on my Honda, for some reason the connector was half loose, not cliped in tight.
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