I am helping my friend fix his his boost gauge and A/F meter lights. The gauges work but the lights does not come on when u turn on the head light or parking lights. I was looking that wiring, almost everything was connected but a ground wire and another wire which i couldnt tell wut it is. I wonder do anyone have the instruction.
-note his car is an 87 TII

 

If you want them to turn on with parking lights or headlights you need 12v accessory wire and a ground. You can tap into the cig lighter bulb wiring. So you need to find out which wire is which. Accessory wire is normally yellow and ground is black. If it's an electric gauge than red is 12v constant.

 

the wires are not black nor yellow. They are clear n purple clear wire. so yea.