[hawkeye18]

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.

 

[Grimace427]

Pretty awesome! I keep a spare GPS antenna in my box that fits most of the cars i work on and I can plug it straight into the NAVI unit for diagnosis. 99% of the time though it's a software/database issue, but it's always good to cover all the bases.

 

[Bryonl]

I don't like to say it, but the days of technicians digging in and shaking wires is over. Now days the technician plugs in a diagnostic tool, reads the fault and fixes that. If no fault comes up they are clueless. Thats not to say all are that way, most are great, some just lack good troubleshooting skills. As aircraft mechanics, we know to dive in and shoot wires. Glad your system got fixed and pat yourself on the back for your troubleshooting skills. C-5s rule cause size matters!:gringreen

 

[Kona stang10]

When investigating an issue always think of the simplest thing. A wire short is a simple thing...

 

[Grimace427]

I don't like to say it, but the days of technicians digging in and shaking wires is over. Now days the technician plugs in a diagnostic tool, reads the fault and fixes that. If no fault comes up they are clueless. Thats not to say all are that way, most are great, some just lack good troubleshooting skills. As aircraft mechanics, we know to dive in and shoot wires. Glad your system got fixed and pat yourself on the back for your troubleshooting skills. C-5s rule cause size matters!:gringreen

Mercedes has been great to me as far as reliable fault code diagnosis, but being the young tech-savvy generation that I am in I get those cars that will have problems upon problems with nary a code to show for them. CAN communication and software compatibility are the most common cause of faults that don't want to cooperate, and can't be fixed with just a wire repair.






Satellite radio can kiss my ass.

 

[txfishingdad]

Thank you for your service Hawkeye, being a former Navy member myself we are all proud of our brothers and sisters!

As an electrical engineer I'm as disgusted by this as you, great job of troubleshooting, it's a lost art!

 

[hawkeye18]

Thanks for all the shout-outs, guys! :bigthumbsup

I took a picture today - this is a 100% crop of what I'm talking about. You can see that even just in three days at least one layer of my electrical tape wrap has been cut through. You can see the shiny spot on the right side of the hole where it was rubbing on.

I tucked it out of the way as you see it now. If it stays a problem, I'll just tape the wire there with some more electrical tape, which I have approximately six million rolls of.

As thanks for looking at this thread, I'll share a picture of my car I took today from three floors up:

And, as a bonus, the reason I was on a third floor landing with a 70-300mm lens in the first place:

I work on those! Well... not that squadron (that's a VAW-120 plane), and not that type (That's a Hawkeye 2000, I work on Nav-UP models), but those! They're pretty neat. I like them. You might've noticed the E-2 sticker on my car. :winks

 

[Grimace427]

For issues like that where wiring is being damaged by a sharp edge I cover the edge with a thick felt tape. It gets sold by the yard so for warranty work even if I only need an inch and get plenty to work with. It's also perfect for rattles and squeaks between interior trim panels.

 

[SOMDStang]

Nice job putting that technical know-how to use! I've had my J-STD soldering cert for a while now too and it's always amusing to open up a piece of electronics and sigh in disbelief at the sad wiring/soldering jobs. It's too bad you had to find it in a stang though :/

 

[pdmustgt]

I don't like to say it, but the days of technicians digging in and shaking wires is over. Now days the technician plugs in a diagnostic tool, reads the fault and fixes that. If no fault comes up they are clueless. Thats not to say all are that way, most are great, some just lack good troubleshooting skills. As aircraft mechanics, we know to dive in and shoot wires. Glad your system got fixed and pat yourself on the back for your troubleshooting skills. C-5s rule cause size matters!:gringreen

I call BS on we techs don't wiggle or dig into wiring. I can tell you first hand it doesn't show the problem. Then other issue with "can's" or computers, software issue that cause problems between hardware. You can ohm out the wires showing ok but remember 1 strand of wire can show it good but cannot carry load or signal. It's not as easy as you think

 

[whirledpeaz]

Hawkeye18,

That's an awesome example of "Questioning to the Void"!