Communication port is not working properly

COM1 and COM2 refer to a computer's communications, or serial, ports. COM1 ports are often used on older PCs to connect network devices, digital cameras and mice. Faulty drivers software that enables the hardware to communicate with the operating system or incorrect hardware configuration can influence COM1 behavior. In rare cases, the expansion card that adds the serial ports to the PC can fail, rendering both COM1 and COM2 ports useless. To repair a COM1 port, you must determine what is preventing the port from working before attempting a solution.

Click "Start." Go to "Control Panel" and then click "Hardware & Sound." Select "Device Manager" from the submenu. Expand "Ports (COM & LPT)." Double-click "COM1." Review Device Status on the General tab to check for problems with the software driver. If the message "The Device Is Working Properly" appears, click "OK" to close the window; otherwise, look up the error message on Microsoft Support. Follow the directions in the Knowledge Base to correct the issue. Press "Alt" and "V" to open View. Scroll to "Resources by Type." Press "Enter." Double-click "Interrupt Request (IRQ)" to see a list of devices. Double-click "Communications Port (COM1)." Check the term to the left of COM1 to see if the card uses an ISA or PCI interface. If the card uses a PCI interface, it can use the same IRQ as another PCI device without producing a hardware conflict. If the device is ISA, it needs its own IRQ. Go to the "Resources" tab. If "No Conflicts" appears in the Conflicting Device List, close the window; otherwise, uncheck "Use Automatic Settings." Click the drop-down menu and select each configuration until the port no longer interferes with another device. If conflicts occur with each configuration, double-click "IRQ"; you may need to try different configurations before Windows gives you permission to edit the interrupt request. Click the up or down arrow to change the IRQ until the message "No Devices Are Conflicting" appears in the Conflict Information field. Click "OK" to close each window. Click "Yes" when prompted. Connect a device to the COM1 port to test the port. If the device doesn't respond, shut down the computer and then unplug the power cable. Disconnect all devices from the back of the PC. Remove the case cover and touch the computer's chassis. Set the computer on its side so that the PCI and ISA cards sit at a 90-degree angle to the floor. Find the serial ports on the back of the PC. Look on the opposite side of the case to find the associated card. Shine a flashlight onto the card and make sure that the copper contacts are not visible. If you can see the contacts, reseat the card in its slot so that it's fully installed to the motherboard. Reassemble the case and boot into Windows to test the COM1 port. If the port still fails to work, you may need to replace the serial port card.