engine coolant temperature does not register on 2006 Chevrolet HHR

this first happened several thousand miles ago, then suddenly started working properly. now again the guage does not read, the "check engine" indicatoe is lit, and the AC does not work.

Asked by for the 2006 Chevrolet HHR
oh the chevy hhr if the coolant is not above 160deg in the first 10 mins of driving it will go into this no temp gauge and ac will not work the computer thinks the car my be over heating so its in a protect mode.
I have replaced the thermostate 5 times in mine now. 2 times it was bad. I just resently replaced the temp sensoir with a new gm part and seems to be working now.
I have the same exact symptom with my 2006 HHR. where is the temp sensor located - is it accessable for not too handy person (me) to replace?
This is the answer that makes sence. I have been having this happen for a couple of years now. It happens when it is cold out.
1 more answer
My 2007 hhr does the same, went 2 times to warranty and it still doing it.