shsd

:blink: For any one interested I have fixed my Sat Nav (C5 2001) The problem showed itself by the Sat Nav positioning the car approximately 30 miles out of position. (see satnav lost at sea). After investigating the CD and software I concluded that the problem was the incoming GPS signal. To test this I checked the geographical infomation display (thanks randombloke) this is supposed to read a signal strength of 3. Mine was reading 1. So the antenna was suspected. To test this I needed a good antenna. As the problem could be either the GPS unit or the roof mounted antenna or the connections in between the two. Step one check continuity of cables. Remove the two screws securing the CD unit lift up the compartment door to ease out the unit. Remove the aerial plug (SMB connector) from the back of the unit. Drop the headlining above the rear seat to expose the connector plug. The GPS conn is the grey one. Step two connect a known good antenna (more later) to the CD unit go for a short drive to establish signal (Check signal strength etc.) This will determine if the problem is the roof base unit or the GPS module. In my case it was the roof base unit. Replace roof base unit with a new one. Note: The GPS antenna is not connected to the radio aerial but is a separate module inside the base unit. The base unit containes three separate modules 1 radio 2 Traffic master 3 GPS. The radio and traffic master are powered by a 12v supply (red wire going in) The GPS module is probably powered by a 3.3v supply fed from the GPS module via the antenna wire. To get a known good antenna I purchased a cheap plug-in module from Maplins electronics £9.99 plus the correct SMB connector for the rear of the CD unit. These units are used in cars when after-market SatNavs have reception problems. On connecting and testing this system my unit relocated the car correctly and signal strength returned to 3. Problem solved!! On buying SMB connectors; unless you have a crimp tool of the correct type buy a clamp type connector.

You are correct there are 4 leads from the aerial, 3 signals comming out and one power going in.

Thanks for the response. Signal strength is low but this means that it could be the tuning circuit within the satnav unit or the antenna it is unlikely to be the CD or the CD player. Just out of interest the aerial base unit for the C5 contains three items. One is the SAtNav antenna also included is what is probably one active filter circuit for the radio and one for the traffic master.

My C5 2001 Sat Nav is currently placing the car in the north sea approximately 30 miles from its actual location. It will track the car's progress but cannot locate the actual car's position. I suspect an aerial fault; has anyone else suffered this problem. It has become progessively worse over the last few months and now seems completely knackered. I have tried a software reboot and cleaned the CD and Reader. I have also checked the aerial base unit for corrosion and checked the continuity of the cable between the base unit and the CD unit. :unsure: