Back at the end of April, I mentioned removing our Raymarine E-120 multi-function chartplotter instrument to return to manufacturer for a repair. The problem is that the back-lighting has been randomly “flashing” to full brightness and back to dark when running at night. This has the very annoying effect of destroying your night vision while at the helm.
When I reported this at the Raymarine online tech support, they suggested it could be a low-voltage situation. But, they suggested sending it in. After paying hefty shipping and insurance fees I sent it off before my backpacking trip. I expected they would fix the problem and ship it back.
Last week, they called and said their tests showed the E-120 is working fine. They recommended a voltage isolator/converter to basically control against surges or voltage drops due to other electrical equipment in my system. After discovering the unit they recommended costs several hundred dollars (this is what they recommended), I wondered if this is an isolated incident or a problem with our electrical system. E-mails to other St. Francis 50 owners, and the manufacturer confirmed they have all seen this annoying problem with the E-120. So, I did some Googling and discovered several other E-120 owners on many different boats have reported the problem. The most common factor seems to be that when the E-120 backlight is in low-light mode (at night), and the alternator regulators are charging the batteries, you get the flashing on the E-120.
The E-120 specs say it can handle 10.2 to 30 volts of power. But, I suspect the backlight system is more sensitive. I’m curious whether there are cheaper voltage isolators which might solve the problem. Time to do more digging… Ahh, the fun process of diagnosis and learning the quirks a complex boating system.
[UPDATE: I found an inexpensive DC-DC converter (it basically regulates the variable power from the boat to a rock-solid 12V at up to 4.2 A). Here's the link - it cost $27. This solved our problem and the E-120 never has never had the problem again. I would recommend this solution for other electronics sensitive to power.]