When you switch on the CPAP machine, you should hear the pump starting, and the green light next to the power switch should turn on.

If this doesn’t happen, there are several things to check.

We’ll start with the ones that are most common and easiest to fix.

First, check that the power cord is plugged firmly into both the CPAP machine and the plug socket.

Try plugging another device into the plug socket to make sure that this is working.

Next, we’ll check the fuses.

There’s one fuse in the plug and two more in the machine.

First check the fuse in the plug. If it’s blackened, change it. Or you can test it with a multimeter.

Set the multimeter to the continuity setting.

Touch the probes together to check what should happen when there’s a continuous circuit. You should hear a high-pitch sound and get a numerical reading on the screen.

If the fuse is ok, the same thing should happen when you touch either end.

If nothing happens or you get the reading ‘OL’, the fuse is blown.

Next check the fuses inside the CPAP. These are located in the power entry module at the back of the CPAP machine.

Use a flat-head screwdriver to press down the catch and prise the fuse holder from the machine. Then remove each of the fuses and test them individually.

If there is no problem with the fuses, the next thing to check is the power supply cable.
Plug the machine into the electrical socket and turn it on. Set the multimeter to the voltage mode.

Carefully insert the multimeter probes into the live and neutral terminals. The multimeter should display a figure which is close to your country’s mains voltage.

If this is not the case, the power supply cable is faulty and will need to be replaced.
If the fuses and power supply cable are OK, we need to now check the electrical components inside the machine.

To do this, you’ll need to open up the CPAP machine. For safety, switch off and unplug the power supply at the wall. Remove the screws around the case and fold open the top panel.

Before going any further, just make sure that all the cables inside are properly connected. If there is a loose cable, it will stop the machine from working.

The electricity enters the power supply module at the back of the machine. It’s then taken through cables to the power switch on the front of the machine. The circuit then goes through the alarm module to the electrical pump.

There could be a fault in any of these. In the next films, we will show you how to systematically check the electrical circuit in the machine.