On the GL1800riders forum some folks devised a simple way to actuate the temperature display by using the turn signal cancel button. While I had my top shelter off for other reasons I decided to add this mod.
This is the wire (light green w/white stripe) from the turn signal cancel switch. These connectors are found forward of the right storage pocket. It will read +5V normally and 0V when the switch is depressed.
This is the wire (blue /yellow stripe) from the temperature display button.
I would normally solder the connections but I was in a hurry.
I added a quick disconnect to the wire just in case it needs to be moved.
Now when you push the turn signal cancel switch the temperature is momentarily displayed.