Upgrading the rear view mirror '08 TB

[tgwright]

This post is for those of you who would like to add the compass, thermometer and auto-dim mirror to your Trailblazers. I just did this to my new '08 TB and I had a difficult time finding the info I needed. I wish someone would have provided this info for me.

I purchased a mirror on ebay that was advertised as an OEM mirror (had the GM part number sticker still on it) which had the onstar and passenger airbag features (like the original mirror), plus the auto-dim, compass, and temperature for about $44 shipped (advertised as new and I believe it was). This turned out to be a plug and play deal AND the wiring for the temperature sensor input was already in the headliner and the mirror plug. I found the other ends of the two temp sensor wires under the hood on the driver's side just behind the battery box along the top of the fender. They were brown and green/black and terminated inside a plug that also has a blue wire. I purchased a sensor on ebay for $26 (has the GM part number on it) that came with the two wire harness plugged into the sensor. I located this sensor using one of the two lower grille attach bolts placing the sensor just behind the grille. I spliced these two wires into the existing wires near the battery box and immediately had temp display on the mirror. A little heat shrink tubing followed by good quality plastic tape finished the job. I now have all of the original displays plus compass, temperature, and the auto-dim action which I really missed when I sold my Tahoe. This was a simple job and should be easy for anyone with a little mechanical skills to do. Good luck.