Sat Nav position query

[McMasters]

Hi Hans
Well I followed up on your suggestion to check the gyro value.
When I started and entered the service menu it sat on 02728.
When I left the park position, left exit, the number reduced to 02426 approx.
As I proceeded along the road straight it wavered between 027-- and 026--
Hard right at low speed it went up to 028--- and when I turned hard left it went down to 019--. (Bit dangerous watching and driving so the last numbers are not recorded.)
As I drive further the on a straight stretch it seemed to hover at the 024500 + or - for a while.
I then drove with the Nav on and the scale at 100m and it was all working OK for awhile then after a small turn left it started the "please return to known route" instructions. When I looked at the map the blue arrow car indicator was of the road map again. This time to the right. It seemed to be going straight ahead and not following left.
As I followed the road it kicked in with the right route instructions again but now I noticed the position of the car was 20 to 30 meters ahead and at one stage had turned left on the correct route before I had arrived in the car. Then the blue arrow was off in the paddocks again. Slowly it found the correct position after I was delayed at the lights.
All very odd. I have ordered a new arial but the service menu always shows 6 to 8 satellites so I am not sure that is the problem.
Any Nav Sat wizz members please feel free to comment. I would like to get it sorted somehow before my better half gets lost somewhere!!

[hans.schaaper]

All the symtoms you describe suggest a faulty gyro.
Obviously it's not dead but could still give unstable (erroneous) readings.

"When I started and entered the service menu it sat on 02728"
I think this indicates an error.

The easiest way to make sure would be to temp. swap it with a known good unit MK3 or MK4.
Suppose that would be easy if you were in the UK.

The other alternative is to have it checked and or repaired here:
Siemens VDO Automotive AG
Repair-Center
Philipsstr. 1
D-35576 Wetzlar
Tel.: +49 6441 - 383 370
Fax: +49 6441 - 370 325

No idea of the financial implications.

You could also try to contact the German based Rover75/MG ZT forum: http://www.r75.info
They are an active club and have regular meetings.

Hans

[McMasters]

Thanks for the not so good news Hans.
I swapped from a Mk2 to Mk3 to get away from Navi problems. Sounds like it is on the way out too, all over but the shovel work. I will try a new antenna when it arrives. I also plan to go on a longer run today.I will check the gyro again.
Some posts suggest that if the unit is relocated it can take a while for to find its new constant location and may need a few weeks. As it came from the UK to Germany maybe it is a bit lost still on the other side of the road !!!??? :-). Clutching at straws here I know but I will give it a go. Too costly to just write off yet.
Any other Nav experts please comment.

[McMasters]

Longer run today , 200km+.
Nav worked OK , no loosing the plot events. No off road experiences no return to route commands. Highways and city work . Maybe they do need time to orientate after being moved from one car to another that is quite a distance. Amazing.
For Hans:Gyro stationary read out on service menu. 02478, and later 02488.

[ChineseRover]

I would not worry too much about the display occasionally showing you off the road. I think this is a problem with the accuracy of the maps. I have driven on lots of minor roads in Germany where the satnav shows me driving in the fields and forests alongside the road. It seems to snap back when I got to junctions.

The only time I have experienced this in the UK is driving down roads with tall building in London, when it can do the same thing, or worse, assume you are on a road running parallel with the road you are actually travelling on.

Originally Posted by lowedb

There isn't actually a compass in the system

Originally Posted by lowedb

You are dead right it does dead reckoning, but it uses wheelspeed pulses and an accelerometer to do this, no compass.

Er very difficult to navigate (er impossible?) by DR without an understanding the direction of travel!