How-To: Change The Color Of Your 99-02 GMT800 HVAC Control Backlights.

geo99 · January 17, 2015

I want to add to the original post by scottieboy found
here,
http://www.gm-trucks.com/forums/topic/102015-change-the-color-of-your-99-02-gmt-800-ac-control-backlights/

I used ready made lights to change the cluster to blue from here,
Partsam 10 Pack PC168 T10 Twist Lock Blue
http://www.amazon.com/gp/product/B00KVC78RU/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

Then I used
Partsam 6x Blue T4 Neo Wedge Instrument Gauges
http://www.amazon.com/gp/product/B00KVXTUL6/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

and modified them for the a/c control back lights.

The LED assemblies have resistors built in, so they need the full 12 volts to function, and are installed in parallel instead of series as was in the original post from scottieboy

First, remove the LED assemblies from the twist lock holder

I then hooked them to a 12 volt source and marked the positive lead with a red marker.

Then I soldered two LEDs in parallel with short lenghts of wire. Then clipped the positive lead of one LED and the negative lead of the other LED short, removing the excess. You will need two of these made up.

Then the old bulbs were removed and and the connection points marked.

Then the two LEDs wired together are soldered to the board, using ONLY the one long positive lead and one negative lead. the LEDs are just held in by one lead each. I kept the LEDs pointing relativly straight up with just a slight downward tilt. you may want to tilt the LED closest to the cold side of temp knob toward the hot side of the knob. Being an LED of single color, the blue side of the display is bright and the red filters out the blue and is almost totally dark.

repeat for the other side. The connections are in the same locations on the other end of the board.