The diaphragm is at the end of the black rod that you see moving back and forth when you turn the device on. If it is damaged, the pump will not suck the air correctly. Because this is a moving part, it is one that most frequently fails.

To replace it, you do not have to take the whole electric pump out, although if you suspect internal fluid damage, you will need to remove the pump anyway to inspect and clean it.

The pump is held in place by three screws, which you take out with a Phillips screwdriver. You don’t need to take these screws out completely to be able to work on the pump.

To remove the diaphragm, you simply pull the end of the black rod out from the pin holding it in place. This allows you to gently remove the diaphragm.

The orange-colored rubber should not be damaged at all. If it is, then the diaphragm needs to be replaced. This one is intact, so can be put back into the device.

To put the diaphragm back, you should gently put it in at an angle and then straighten it. Push it in until the small eye hole at the end of the black plastic rod aligns with the pin. Push it back into place. There should be a click.

The other part which you may need to check and replace if damaged is a rubber gasket behind the entry and exit nozzles. To access this, gently prise the two nozzles off with a screwdriver.

You can take the gasket out to inspect it. If there is any damage, you should replace it.

You should clean where the gasket fits and inside the nozzle unit with cotton and alcohol.

When you put the gasket back, there are two small guide holes to make sure you put it in the right way around.

Likewise, the nozzle unit itself will only go back in the correct position with the nozzles facing outwards. You simply press it hard to click it back into place.

You would now put the motor back and test it before reassembling the rest of the device.