If your device is turned on but won’t suck anything up, try emptying your dust cap of any debris regularly or replacing it if it is very old. Also check to see if there’s is any build up in the vacuum tube by turning off the device and checking with a flashlight. If you find anything, just use a long and dull stick to remove it. If the problem persists you may have a tear in your vacuum hole, so follow the guides to remove it.
There are only a few slight differences in the HV300 series of vacuums. The HV300 is the lowest model, and has a 27 foot power cord while the HV301 and HV302 both come with 30 foot cords. Other than that, the differences are the number of accessories each one comes with. So, repair on the vacuum should be identical for all three in the HV300 series.