This is what I used to see all the damn time. Driving through the middle of the Chesapeake Bay. Driving through runways. Lost in neighborhoods I've never seen or heard of before. It was infuriating to me that my $2000 navigation system not work.
I found the Nav system diagnostics suite and used it to get a look at my GPS status. This is what I sometimes got, though it was usually less than two:
You need an absolute minimum of three GPS satellites to gain a fix. You want at least 5 or 6 to get an accurate fix. No good.
I took the car to the dealer, who agreed that something was wrong. They kept the car for three (three!!) weeks and gave it back to me saying they couldn't get it to break. Well, truth be told, it did work pretty well for about two days... but then it started not working again (I think I now know why).
I lived on, frustrated and dejected, never trusting my GPS to guide me where I needed to go.
The worst part of all of this is, I'm an avionics technician for E-2C Hawkeyes - which use not one but two separate GPS systems! You'd think I'd be better at fixing my own. To be fair, though, I don't get to spend the Navy's money to replace my own parts.
We had a situation at work a few days ago where a failure was caused by a wire chafing against bare metal, and the shield shorting against the chassis of the aircraft. This got me thinking - what if wiring was the cause of my own GPS failures?
So, one day earlier this week, I took the cover off my trunk lid and saw if I could find anything wrong with the GPS antenna or its wiring. I took the GPS antenna off the trunk (very easy, btw - one 10mm bolt and it's off) and took it apart.
What I saw inside the antenna disgusted me. See, I'm a solder technician as well, and have been trained to near-NASA standards for soldering reliability and quality, so to see the face of the antenna and its metal shield covered in left-over flux and its corrosion byproducts was also pretty saddening, but I cleaned it all up as best I could.
Then I saw it. The cut. The wire coming from the antenna had a small, but obvious cut in its shielding. I wondered to myself, could this be the cause of all my troubles?
So, I reinstalled the antenna on the trunk, and sure enough, where the wire comes out of the antenna and comes through the bottom of the trunk lid, is an access hole that really ought have a grommet on it - but didn't. The cut on the wire precisely matched the edge of that hole. This meant the shielding of the antenna line was shorting against the chassis and introducing all sorts of fun EMI in the antenna. Bingo!
So I wrapped about eight layers of electrical tape over the nick, and placed the wire back in its original spot; the electrical tape lay on the edge of the hole. I reinstalled the trunk lid liner, and haven't had any GPS issues in the past four days.
I'll attempt to get some pictures when it's warmer and sunnier out.
tl;dr - if you have GPS issues, I feel bad for you son, I got 99 issues but a nick ain't one.