Please take a moment to go through these steps:

Symptom: The system is not turning on or some components are turning on but others are not.

IMPORTANT: Pay special attention to #1 below. YOU MAY NOT HAVE A PROBLEM AT ALL. It’s worth checking.

1. Is the system off because the pressure in the tank is above the low setpoint? What is the tank pressure right now? If the pressure is above the low setpoint (greater than 30 PSI for the Standard, greater than 100 PSI for the Mighty Mite, MAX, Titan 1 and Titan 2), the compressor will NOT turn on until the pressure falls BELOW the low setpoint. This is a safety mechanism that prevents the compressor from straining against high tank pressure during startup. The "fix" is to use oxygen, causing the tank pressure to drop below the low setpoint, at which point the charging cycle will begin.
    
2. Is the system plugged in and powered on? Check the circuit breaker panel for tripped breakers. Recent models (since October 2018) have a green LED on the circuit board. To see it, you must open the lid of the headbox. If the LED is lit, the headbox has power. Are the oxygen concentrators getting power? Read on.
    
3. Are the coaxial cables attached to the right components and hand-tightened? There should be a coaxial cable running from the headbox to the relay box. If you have multiple relay boxes, you can daisy-chain the signal from one relay box to the next using the second coaxial connector. If you have a Drone, you’ll also need a cable running from a relay box to the Drone’s coaxial connector.
   NOTE: The coaxial cable(s) should only be hand-tightened, but firmly attached. You can use a wrench but be very gentle — over-tightening can strip the threads. If tightening doesn’t help, you may want to try a new coaxial cable.
    
4. Do you have sufficient power? For North American systems, each headbox (Main and Drone) requires a dedicated 15 amp circuit (unless you have the Titan 2 compressor, in which case you will require a 240VAC/15A circuit per Main & Drone). Each 3-outlet relay box requires a dedicated 20 amp circuit. Each 5-outlet relay box requires a dedicated 30 amp circuit. If the circuits are not dedicated, other non-HVO devices may be using power and reducing the available amperage.

Symptom: System not filling as fast as normal

The HVO System compressors are equipped with a “dump valve”, which is a solenoid attached the compressor. Its purpose is to enable the compressor to start without resistance caused by built-up pressure. The dump valve is attached to an oxygen exhaust line that runs through a hole in the center of the headbox.

Reach under the headbox and find this line.

NOTE: For Pro Series™ and Pro Plus™ customers, there are two lines that vent under the headbox: one for dump valve exhaust and the other for oxygen sensor exhaust. If the compressor is running and there is a significant flow of gas coming from the dump valve exhaust line, this may indicate that the dump valve is malfunctioning. If you discover this symptom, contact HVO support.
 

Another potential issue can come from the compressor particle filter. If you have a MAX compressor, open the headbox and find the bell-shaped particle filter. This component is situated on the silver bar on top of the compressor (see photo below). If the particle filter is not in the position shown in the photo, you can move it into that position without any tools. In addition, the black part is threaded. If it is loose, the filter will leak. Hand tighten clockwise to ensure that it is firmly closed.

Symptom: Oxygen percentage is lower than normal

1. Are all connections from the individual oxygen concentrators secure (this is usually a brass nut attached to a 1/4" flexible line), seated correctly, and hand-tightened? Poorly seated fittings can allow air to be drawn in which can dilute the purity of stored oxygen.
    
2. Are all of your oxygen concentrators turned on when the system is charging? Do this test while the HVO System is charging (i.e. the tank pressure is below the low setpoint): check the power switch on each concentrator, look for warning lights or audible alarms. Check your circuit breaker panel for tripped breakers.
    
3. Are there any line leaks? Check all oxygen line fittings (barbed fittings, push-to-connect fittings, manifold plugs) to ensure that they are firmly connected. Gently check to see that the brass fittings are seated correctly on the barbs of the oxygen concentrators. Bubble test lines and fittings that are not near electronics.