Rebreathers are complex devices that rely on numerous components to function correctly. When you encounter a problem, it’s valuable to isolate the issue to a specific component before seeking service. The idea is to verify whether a certain issue occurs with different peripherals or different head electronics.
In analog systems, the monitor—such as the Petrel, Nerd, or LED HUD—connects directly to the oxygen sensors via a cable. This cable may use an AK-style 4-pin or a Fischer 7-pin connector and can be unplugged, or it might be “hard-wired” (not intended to be user-disconnected).
In digital DiveCAN systems, each monitor or controller (Petrel, Nerd, or LED HUD) connects to a PCB in the rebreather head, which interfaces with the oxygen sensors and other components (e.g., a solenoid). The link between the monitor and head electronics is typically a 5-pin DiveCAN cable (some DiveCAN rebreathers utilize proprietary connectors). DiveCAN heads require their own power source (one or more batteries).
For more information, see the article Fundamentals of Shearwater Rebreather Electronics
To troubleshoot effectively, try to isolate the issue to either the Handset/HUD or the head electronics side of the system. Occasionally, both sides may be affected; for example, a leak in a Fischer connector can compromise the connection to both the head and the monitor.
While isolation can be challenging, a practical first step is to borrow another rebreather from a friend or dive buddy to swap the Handset/HUD. This helps identify the source of the problem. If the borrowed Handset/HUD operates correctly with your rebreather head, the issue most likely lies within the Handset/HUD. Conversely, if problems persist with the different Handset/HUD, the rebreather head is likely at fault.
In analog systems, detachable monitors (with compatible connectors) can generally be swapped between rebreathers, provided they share the same connector type. Regrettably, “hard-wired” monitors are less flexible for isolation.
Diagnosing an issue can be more complex in dual DiveCAN systems (separate controller and monitor buses), but you can gain insights by swapping Handsets/HUDs with other rebreathers or temporarily swapping the controller and monitor on the unit in question. In these setups, the two digital sides are electrically isolated, so issues will typically be confined to one side or the other.
In hybrid systems with one digital DiveCAN controller and one analog monitor, you usually can’t swap components. Instead, test using different peripherals or another rebreather head.
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Written by Jose Ventura, Shearwater Rebreather OEM Specialist
Cover Photo by DIVEWELLS | © Carolina Wells
