a fan test device to connect a motherboard and a fan includes a power terminal , a first diode , a second diode , a control chip , a first connector , a second connector , a first electronic switch and a second electronic switch . the control chip is connected to signal pins and sensing pins of the first and second connectors . the first electronic switch is connected between the control chip and a power pin of the first connector . the second electronic switch is connected between the control chip and a power pin of the second connector . the control chip outputs different signals corresponding to the connection of the first and second connectors .