GPS Antenna fix issue

[Simi 60]

The plotter is a 2008 SEIWA explorer 3 so I cant see it being out of date.
I can find nothing regarding factory reset in the manual.
Best I could find was "System Test" which is "with unit off hold any key and press power and a new menu will appear on the screen" .
All that happened when I did this was my 12v screen went black and I never got it back.
Same VGA cable into a spare 240v lcd screen has it working again, unplug, put back in 12v screen and still black.
When I turn plotter off, "No Signal" shows on the 12v screen which to me says its working.
Old screen anyway and well past its use by date so not that concerned.

Trying System Test on the new(er) screen and I get no "New Menu" appearing as advertised.

I have sent off an email to SEIWA hoping for some answers and I have a new SEIWA Smart antenna turning up in a few days bought on eBay for $100.
Hopefully that may make things better, if not I have a spare.

[Simi 60]

Today we had a win.
Bit of back and forth via email to Seiwa and I did a RAM clear.

Now the satellites look like this
hdop used to be 4.5ish, now its 0.9 so accuracy increase to boot.

[hellosailor]

There is an issue that mainly used to affect some poorly designed software, where the system did not perform "garbage collection" properly and as a result, outdated data filled (corrupted) some memory areas. Typically you still see this when smartphones and tablets just seem to run slower and slower, until you reboot them and they're all perky again.

Sounds like there is a similar issue in your GPS, and it might be prudent to save that procedure, and perform it once a month, or once a voyage, etc. at convenient times. Because the same problem could be subtly corrupting your GPS data, as you noticed the accuracy improved afterwards as well.