If you guys have read my posts on this subject I have explained how the light and gauge are wired. Here is a diagram that shows the circuit board and how the light and gauge wiring is connected.
Notice the dashed red line on the left that was connected to pin five on the light dash. The green wire that was connected there was moved to pin 6 for the gauge dashes, and nothing is connected there. It's one of the changes that has to be made when changing dashes.
It's already been said that the key grounds one side of the light when the key is turned to start. This is to test the light. It does the same thing to the brake warning light on both types of dashes.
I've got two gauge clusters and I'll have to check to see if the temp light came installed with them.