A relay is a fancy word for a switch. Your interior switch sends 12 volts to the relay that activates the relay (turns on the switch). You troubleshoot it like any other switch. Is 12 volts coming out of the relay? If not the relay is bad, if so is the voltage getting to the motors? If so it's the motor or jammed linkage. If not it's between the relay and the motor.
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A relay is a fancy word for a switch. Your interior switch sends 12 volts to the relay that activates the relay (turns on the switch). You troubleshoot it like any other switch. Is 12 volts coming out of the relay? If not the relay is bad, if so is the voltage getting to the motors? If so it's the motor or jammed linkage. If not it's between the relay and the motor.