How to diagnose chartplotter/GPS issue

[leecea]

I have a small Raymarine Axiom plotter that is networked to other instruments and was all installed by the previous owner. It has all worked fine for the last three years. There has always been a slight startup delay while the plotter acquires a GPS fix - that seems normal.

Recently that delay seems to have become longer and on two occasions I had to turn everything off and back on for it get a GPS fix at all. Once it has a fix it works fine. There are no error messages, unless they are somewhere not obvious.

I am trying to determine what I should investigate and in what order. Seems like it could be a few things:

- The chartplotter needs a software update (I have never done one)
- The GPS unit is malfunctioning somehow
- There is a poor network connection somewhere (note that when this happens the plotter does show depth so I assume it means it is on the network).

Can anyone suggest the best order in which to troubleshoot this?

Thanks.

[Calif.Ted]

It's #2 (malfunction) and #1 would be first best cure.
Last plotter failure I experienced was as you describe, started taking longer for initial position. Checking tides I discovered that the date was wrong, it had retreated to date of manufacture. Only cure was a software update that was no longer available. Plotter continued to get worse like it had Alzheimer's until it decided to just shut down whenever most needed.
So first check and see what date it thinks it is and go from there.

[sailingharry]

A critical question that would be helpful is the source of GPS data.
Many, if not most, chartplotters have internal GPS. They either use an internal or external antenna, but the signal processing is done in the unit. In this case, failure to obtain a GPS fix is either a compromised signal (something placed over the antenna?) or an internal failure in the calculation subsystem.
Some, such as my Furuno, have no GPS capability built in. The GPS is an external source, by default a N2K receiver. This is a mushroom on the arch that not only receives the signal, but processes it and turns it into N2K data. In my case, a loss of GPS data could reflect a problem with the antenna or the network, but likely is not related to the charplotter itself.
Do you know how your unit gets a GPS fix?

[Rohan]

Originally Posted by sailingharry

Do you know how your unit gets a GPS fix?

The Raymarine Axiom series all have internal GPS.

My guess is either the internal GPS is damaged or there's small short circuit somewhere that's interfering.

Another possibility is local equipment interfering with your GPS signal.

[Takamoana]

Not sure about Raymarine but my old Garmin had a button battery that maintained the memory. When the battery died, it had to initialise with no memory of the last position so took quite a while. The battery needed to be changed every few years but was a simple procedure.