Sat Nav thinks I'm miles away

The_Laird · #1 16th February 2011, 06:19 PM

Back in my A8 today, hoping to secure a sale, but the sat nav didn't work properly. According to the arrow on the map, it positions me around 20 miles away and the display in the instrument cluster says I'm 'off road'.

Any ideas guys?

Singh · #2 16th February 2011, 07:52 PM

Glad people are interested, its a lovely car just a slow market. Did you take it for a thorough drive. When I first set my RNS E up it was about half a mile out then after a quick drive it collaborated and has been perfect ever since. It may also be the GPS antenna at the back I read once water got into one which caused problems. Are you able to Vag Com?

PsYcHe · #3 16th February 2011, 08:50 PM

It'll lose it's position and tracking data after a whiel and could take up to 30 mins to re-fix.

Adrian E · #4 16th February 2011, 09:40 PM

Best way for GPS to get a fix is park somewhere nice and open (no tall buildings etc) and leave the sat-nav running without moving the car. As soon as you drive off it increases the time to get a fix by a country mile. Shouldn't take more than a few minutes.

The sat-nav will look for where it expect the satellites to be, but if that was more than a couple of days ago it'll be looking in the wrong place. Eventually it figures it out and then knows where to look the next time.

On my TomTom you get a weekly download telling it where to look for the satellites on a given date.

The_Laird · #5 17th February 2011, 07:14 AM

Thanks for the advice guys.

I think the sat nav is finding satellites as it does show an arrow on the map and come up with distance and time to destination. Now and again, it also thinks I'm back 'on road' and briefly gives directions. The problem is, the arrow is about 20 miles from where I am and not usually on a road.

So, after trawling through earlier threads on this topic, I'm going to get the GPS box off and see if it's wet - it did lie covered in snow for ages.

Does anyone know how to get the boot lid trim off to access the GPS?

PsYcHe · #6 17th February 2011, 08:40 AM

It's pretty simple.. You just unscrew everything that's attached, then hunt down all the carpet covered screws that hold the liner in place, then it pretty much falls off from there.

The_Laird · #7 19th February 2011, 08:22 PM

Thanks for the help (yet again!).

When I took the wee box off the boot lid, it did seem a liitle damp - but no amount of appication of the hair dryer improved the 'lost' sat nav.

So, then I went rambling thorough the sat nav menus and eventually found a section where you can manually set your location. After a couple of 'careless' atempts, I managed to let the sat nav know where it was and, I think, got it all sorted.

In hindsight, I wonder if this was a result of a serious battery failure (new battery since installed) and the system simply needed to be re-set?

Greg66 · #8 8th May 2011, 10:51 AM

This may be too late for the op, but might help someone else with a similar issue.

The symptoms described sound like a classic case of GPS antenna failure. To check this, both the RNS-D and RNS-E have tucked away a reading that tells you how many satellites they are picking up. 4 or 5 is normal. Zero probably means the GPS antenna isn't working.

The sat nav will sort of work even if this state if you tell it where you are. The car has internal gyroscopes which it can use to determine its movement, and it can snap the estimated position to a grid (ie the sat nav map). However, the further you go, the greater error creeps in, and the more and more you will lose position.

To replace the GPS antenna you have two choices. The first is to source a coloured coded replacement and replace the "puck" on the boot lid. Although I haven't tried this (due to cost), I understand there is a connector in the nearside rear pillar.

The second is a DIY fix. You source (1) a GPS antenna from eBay (search eBay for A8 gps antenna or something similar); (2) the RNS-D/E removal keys (also eBay); (3) a small self adhesive Velcro patch. Total cost should be <£20.

Note that the sockets on the D and E differ. On the D the socket is a round female socket. On the E it is a blue plastic clip in affair (sold on eBay as a fakra connector). A plug that is designed to fit a D will fit an E, but I wouldn't be so sure that a fakra plug will fit a D.

Getting the RNS unit out and plugging in the new antenna is easy (just unplug the old one and leave the cable). You can leave the RNS connected and switched on throughout.

Siting the antenna ideally requires line of sight to the sky. For this reason stuffing it in behind the RNS will not work very well. The best site I have found is inside the "hood" above the instrument cluster. Getting the instrument cluster out is very easy - google is your friend. You do *not* have to disconnect it from anything, just get it far enough out on the RNS side so that you can get a hand in behind it and up towards the inside of the "hood". Pop a Velcro tab inside the hood and another one on the GPS antenna, site the antenna and replace the cluster. It's a good idea to replace the cluster before the RNS so that you leave enough cable to be able to get the RNS out in the future if need be.

20 minute job tops.