Is your Apple Watch Series (42mm – Series 1) not reading your heart rate properly? Check your heart rate from some other device. If there is any discrepancy between the two and if the other machine is in perfect order- then there is some issue with your watch only. Apple watch comes with a heart rate flex cable that helps the device to read the heart rate. But if there is any problem with the cable, you will only receive erroneous readings. Thus, it seems the heart rate flex cable of your Apple watch needs to be fixed. No worries, our replacement Apple Watch (42mm – Series 1) Heart Rate Flex Cable will take care of your issues here.