First and foremost, before mucking about with your vessel electrical system
(for anything, but especially for a safety
device like an AP), become intimately familiar with ABYC E11 - AC and DC Electrical
Systems on Boats, and/or NMEA
standards for vessel wiring
and proper DC grounding methods.
is the # 1 cause of electrical
failures. (Everything else is a very distant second.)
Most AP dropouts to standby are due to low voltage. If the condition never happens, or happens less frequently when the engine
is running (with alternator
charge voltage connected to the battery powering the AP), this is almost definitely a power issue.
(An off-course drop-out results in an "off-course" display and beep. These too are often due to poor installation
or operator error, including extremely poor sail trim.)
Many DIY installations suffer this problem, and some "yard technician" installations also suffer.
The first step is to measure the voltage at the course computer (if equipped) and/or display head
, WHILE HIGH CURRENT
DC LOADS SUCH AS REFRIGERATION
, INVERTERS, AND AP MOTORS ARE SWITCHING ON.
(ST4000+ and earlier models had the course computer in the display head
, newer models are separate.)
In almost all cases, the culprit it too small wire, bad connections, or poor ground and grounding. (If you don't know the difference between "ground" and "grounding", go back to paragraph # 1.
For all instrumentation, the power wiring
chosen should cause no more than 3% voltage drop OVER THE LOOP LENGTH. ie If your battery terminal voltage is 12.80, your voltage at the + terminal on the instrument (WRT the negative battery terminal), should be no less than 12.61 (if the device + terminal is in the middle of the power cable loop).
Note that some switches and breakers, especially when they get older (but even some brand new) can have high impedance contacts, which will cause excessive voltage drop.
STOP USING CHEAP
DC DISTRIBUTION PANELS
TO POWER SAFETY
EQUIPMENT! (I can't say this loud enough.) Would you buy a low quality, discount parachute, from a non-reputable supplier? Your instrumentation may be just as important to your safety.
The power cable should be as short as possible while being routed properly (away from AC cables
and high current DC cables).
One also must watch the cable from the battery to the distribution panel. This should be very large gauge and as short as possible.
An AP is a safety device, someday (perhaps every day), you or crew may count on it (with your life) to work properly. All connections beyond the distribution panel should be waterproof (including the connections at the display head). For older models with stab on bayonet connections, seal them with RTV (silicone sealant) after verifying good connections. For any terminal block connections, seal them the same way. (The RTV can be removed if ever needed, but properly sealed one will rarely need to, until it is time to upgrade the electronics
.) Newer display models, powered by the Seatalk NG network come with waterproof connectors WHEN CONNECTED PROPERLY (twist till they click and no further).
Another (remote) possibility is EMI (electromagnetic interference). Many jump to this first, not wishing to entertain that they may have botched the power wiring. Power wiring is the problem 98% of the time.
Ensure EMC instructions are followed. Use the ferrites supplied or recommended.
Investigate EMI possibility AFTER every possible low voltage possibility has been eliminated.
Lastly, it is possible the unit could be defective. People tend to jump to this conclusion first, but if the weatherproof case has not been compromised, and the unit is less than 20 years old, it is rarely the issue.
We expect our brand new home entertainment electronics to work reliably for about 6-8 years. They are kept in a pretty tame environment
compared to a cockpit
. Sometimes we are disappointed.
If your vessel instrumentation is more than 15 years old and giving you trouble, maybe it's time...
Installer: # Ray1918