Sat nav losing location - changing a GPS antenna?

[Dr Who]

After hitting a big pothole one dark night, big bang, my sat nav started misbehaving, sometimes thinking it was miles away from real location. I changed the whole sat nav box itself for a used replacement (2011 mk3 avensis 2.0 DVD) to fit the console. No change, loses location when in the slightest weak GPS signal area, like cities, or rural roads through woodland. Think the pothole has probably shaken up the GPS antenna? So, trying to get to it to change it. It lives under the dashboard centre, so far forward it is almost up to the windscreen! So I need to lift the dash itself. Trouble. It unclips in the cabin both sides at the doors, with a quick pull upwards, but there is something holding it down in the middle area, about six inches back, in at least two places. Can't really see what it is, frustrating. 

Anyone know how to lift the dash on a mk3 avensis, or an easy way to change the antenna?

[JiiN]

I had similar problem when I upgraded my cd-player to sat nav. I took that back plate away from sat nav antenna and it went crazy (sometimes it showed I drove at sea, lake, forest etc). After I placed that back plate back to antenna it been very accurate. 

 

Here is some kind of a installation manuals where You can see that antenna:

https://www.toyota-tech.eu/aimuploads/cfbe5c45-90d8-4923-aab2-bef842c50c47/Avensis_RHD_Toyota_Touch_2_with_Go_PZ490_0033x_00_AIM_003_196_2 .pdf

https://www.toyota-tech.eu/aimuploads/cc7189e3-c836-414a-bc21-9b8935c9887c/Avensis_Touch_and_Go_RHD_PZ490_00331_00_AIM_002_323_1.pdf

[Dr Who]

Hello Jarkko. Really interesting. Both the documents you listed seem to show the new antenna held by sticky-pad inside the speedo/rev enclosure, onto the top right. That is SO much easier to get to than the existing location at extreme centre-forward. I have the older satnav, model TNS510, which uses the white back plate you show. I can't easily get to it, but if all I am doing is releasing a couple of screws with a long screwdriver and pulling on the cable to get the plate and old antenna back into reach, that should be do-able. I think you are suggesting using the plate as a base for the new antenna, but sticky-pad held inside the speedo/rev enclosure?

Would I need to use the old type antenna, I'm not sure the plug is the same as the Touch/Go uses?

If I need to buy a tested working old antenna, this usually comes on the white base, so I can just leave the existing one sitting at extreme centre-forward?

[JiiN]

Hi Paul!

Im not sure how it works with TNS510 but here is some instruction about TNS350 https://www.toyota-tech.eu/aimuploads/{AE1F9077-2CB4-E4F1-3CDE-E536C2982CB4}/Avensis_TNS350RHD_PZ445-00334-00_AIM002149-0.pdf

That manual also shows to install antenna top of speedo trim. I think I placed mine top of those ventilation pipes behind to radio or somewhere there with sticky-pad (cant remember surely 'cause it was almost three years ago).

That back plate is somekind of a reflector or something like that which gives antenna better signal. There is a metal plate between that plastic and antenna so it is indeed needed to leave there.

I don't know is antenna from Touch/Go compatible to TNS510 but it is maybe easiest way to get working antenna and leave old one there and place "new" antenna some other place.

[Dr Who]

Thank you Jarkko. So, I have ordered a used 8686020080 GPS antenna (with built-in amp) for my TNS510 on eBay. That is one of two similar models available, marked 53 or 54, both seem to be used on the TNS510, around year 2010/11 T27 Avensis, 54 slightly later so gone for that. That comes complete with the tray and plastic surround, so I will unclip the flat plate and just use that. Won't have it for about a week apparently, so have put the car back together so usable.  Meantime will get some double sided sticky foam pads (already have some carpet tape, double sided and really strong but no foam centre, so no impact absorption).

Thanks again for the TNS350 link, quite a few differences to TNS510, but again they are hiding the GPS antenna behind the speedo/rev cluster, so that is where I will stick the new screening plate (it may be an 'earth plane', reflector as you say?) and antenna. The old stuff can just stay put.

Grateful for your help, useful to have someone who has trodden a similar path already. I'll let you know how it all works out!

Paul

 

[Dr Who]

Hello Jarkko. Slipped off a wet roof and broke my leg in October, so didn't get round to changing antenna and testing in weak signal areas.

Have now done this! Fitted a used antenna from a well known 'internet auction house', same antenna but slightly later model. Removed the speedo cluster and fitted the antenna as far back as possible towards the windscreen, adhered with with double sided carpet tape, either side of a sheet of thin flexible foam for vibration/impact resistance.

Have now been using this in several locations with known weak signal, and it has never failed to solidly know where the vehicle is located. Also, sat nav is behaving slightly differently, in that the blue 'route line' moves more often than with the old antenna, as if the sat nav decoder is reading more antenna signal changes. (Not 100% sure that is the reason, just know there is an increase in the rate of updates of the display).

So, the 'new' antenna works well in the new position behind speedo, and no more relocation of 'current location'. Very pleased!

Thanks again for your help.

Paul