turn the car off. unplug the small red wire. turn the key on, don't start. use a meter and test for 12v on the red wire. the dash light should be on. no 12v-pull the cluster and check the bulb AND check the wiring to the alternator. unbolt the blue ground wire and check it carefully for breaks. the 8v reading sounds like a big voltage drop. all the connections have to be clean and tight. good luck, chuck.